QVAC-20987 feat[api]: add llm reasoning budget caps

[zoq]

🎯 What problem does this PR solve?

• Makes llm-llamacpp reasoning-channel control more useful by allowing positive reasoning_budget values to cap <think> output instead of only supporting unrestricted/disabled modes.
• Aligns reasoning-budget sampling with template-provided thinking tags so Qwen/Gemma-style chat templates can expose balanced reasoning output without hard-coded <think> assumptions.
• Hardens backend defaults and CI coverage around flash attention, OpenCL KV-cache support, mobile grouping, and long-running integration tests.

📝 How does it solve it?

• Extends load-time and per-request reasoning_budget parsing so -1 is unrestricted, 0 disables thinking, and positive integers cap the reasoning channel at that many tokens.
• Exports thinking start/end metadata from chat-template formatting, reconfigures the common sampler with those template-specific tags, and emits the matching visible forced-open reasoning text.
• Defaults flash attention on for non-BitNet/non-finetuning models, while rejecting unsupported quantized KV-cache types on OpenCL with an early validation error.
• Refreshes llm-llamacpp tests and platform scheduling: reasoning-budget unit/model coverage, chat-template helper coverage, tools-compact session flush fencing, continuous-batching mobile wiring, Windows/macOS skip adjustments, and VLM performance skip cleanup.

🧪 How was it tested?

• Added C++ unit coverage for generation-parameter override application, positive reasoning budgets, chat-template thinking metadata, forced-open reasoning text, and tune-config backend defaults.
• Added/updated integration coverage for per-request reasoning budgets, tools-compact session persistence, continuous batching, sliding-context overflow, multi-instance/multi-GPU scheduling, and VLM perf test platform skips.
• Verified the PR diff has no whitespace/conflict-marker issues with git diff --check upstream/main...HEAD.

💥 Breaking Changes

• OpenCL now rejects quantized KV-cache types (q4_*, q5_*, q8_0, iq4_nl, tbq*, pq*) during config validation. Use f32, f16, or bf16 on OpenCL, or switch to Vulkan/CPU for quantized KV-cache modes.

🔌 API Changes

await model.run(prompt, {
  generationParams: {
    reasoning_budget: 128
  }
})

Positive reasoning_budget values now cap the reasoning channel. -1 keeps reasoning unrestricted and 0 disables it.

---

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  • https://app.asana.com/0/0/1215284918905450
  • https://app.asana.com/0/0/1215918493007001

[github-actions]

🧪 C++ Test Coverage Report

Coverage:

📊 Detailed Coverage

Filename                         Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NmtLazyInitializeBackend.cpp          99                20    79.80%          11                 1    90.91%         157                36    77.07%          66                21    68.18%
NmtLazyInitializeBackend.hpp           2                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
TranslationModel.cpp                 296               168    43.24%          28                 8    71.43%         506               213    57.91%         181               122    32.60%
TranslationModel.hpp                   1                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
nmt.cpp                               72                22    69.44%           9                 1    88.89%         137                28    79.56%          44                16    63.64%
nmt.hpp                               51                 4    92.16%          11                 2    81.82%          53                 4    92.45%          28                 0   100.00%
nmt_beam_search.cpp                  116                25    78.45%          10                 3    70.00%         254                32    87.40%          76                19    75.00%
nmt_graph_decoder.cpp                164                78    52.44%          15                 7    53.33%         540               161    70.19%         112                69    38.39%
nmt_graph_encoder.cpp                 54                13    75.93%           3                 0   100.00%         268                33    87.69%          37                16    56.76%
nmt_loader.cpp                       270                67    75.19%          14                 0   100.00%         774                97    87.47%         161                67    58.39%
nmt_state_backend.cpp                253                94    62.85%          21                 0   100.00%         489               128    73.82%         165                87    47.27%
nmt_tokenization.cpp                  88                21    76.14%           8                 0   100.00%         135                36    73.33%          61                26    57.38%
nmt_utils.cpp                        120                89    25.83%           8                 3    62.50%         180               134    25.56%          78                63    19.23%
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                               1586               601    62.11%         140                25    82.14%        3495               902    74.19%        1009               506    49.85%

[github-actions]

🧪 C++ Test Coverage Report

Coverage:

📊 Detailed Coverage

Filename                         Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NmtLazyInitializeBackend.cpp          99                20    79.80%          11                 1    90.91%         157                36    77.07%          66                21    68.18%
NmtLazyInitializeBackend.hpp           2                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
TranslationModel.cpp                 296               168    43.24%          28                 8    71.43%         506               213    57.91%         181               122    32.60%
TranslationModel.hpp                   1                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
nmt.cpp                               72                22    69.44%           9                 1    88.89%         137                28    79.56%          44                16    63.64%
nmt.hpp                               51                 4    92.16%          11                 2    81.82%          53                 4    92.45%          28                 0   100.00%
nmt_beam_search.cpp                  116                25    78.45%          10                 3    70.00%         254                32    87.40%          76                19    75.00%
nmt_graph_decoder.cpp                164                78    52.44%          15                 7    53.33%         540               161    70.19%         112                69    38.39%
nmt_graph_encoder.cpp                 54                13    75.93%           3                 0   100.00%         268                33    87.69%          37                16    56.76%
nmt_loader.cpp                       270                67    75.19%          14                 0   100.00%         774                97    87.47%         161                67    58.39%
nmt_state_backend.cpp                253                94    62.85%          21                 0   100.00%         489               128    73.82%         165                87    47.27%
nmt_tokenization.cpp                  88                21    76.14%           8                 0   100.00%         135                36    73.33%          61                26    57.38%
nmt_utils.cpp                        120                89    25.83%           8                 3    62.50%         180               134    25.56%          78                63    19.23%
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                               1586               601    62.11%         140                25    82.14%        3495               902    74.19%        1009               506    49.85%

[gianni-cor]

Removed quantized KVcache test for OpenCL cause openCL backend has several issues with that. tracked on the fabric PR, but will not be added here

[github-actions]

Tier-based Approval Status

**PR Tier:** TIER1

**Current Status:** ❌ PENDING

**Requirements:**
- 1 Team Member approval ❌ (0/1)
- 1 Team Lead OR Management approval ❌ (0/1)



---
*This comment is automatically updated when reviews change.*

[github-actions]

🧪 C++ Test Coverage Report

Coverage:

📊 Detailed Coverage

Filename                         Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NmtLazyInitializeBackend.cpp          99                20    79.80%          11                 1    90.91%         157                36    77.07%          66                21    68.18%
NmtLazyInitializeBackend.hpp           2                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
TranslationModel.cpp                 296               168    43.24%          28                 8    71.43%         506               213    57.91%         181               122    32.60%
TranslationModel.hpp                   1                 0   100.00%           1                 0   100.00%           1                 0   100.00%           0                 0         -
nmt.cpp                               72                22    69.44%           9                 1    88.89%         137                28    79.56%          44                16    63.64%
nmt.hpp                               51                 4    92.16%          11                 2    81.82%          53                 4    92.45%          28                 0   100.00%
nmt_beam_search.cpp                  116                25    78.45%          10                 3    70.00%         254                32    87.40%          76                19    75.00%
nmt_graph_decoder.cpp                164                78    52.44%          15                 7    53.33%         540               161    70.19%         112                69    38.39%
nmt_graph_encoder.cpp                 54                13    75.93%           3                 0   100.00%         268                33    87.69%          37                16    56.76%
nmt_loader.cpp                       270                67    75.19%          14                 0   100.00%         774                97    87.47%         161                67    58.39%
nmt_state_backend.cpp                253                94    62.85%          21                 0   100.00%         489               128    73.82%         165                87    47.27%
nmt_tokenization.cpp                  88                21    76.14%           8                 0   100.00%         135                36    73.33%          61                26    57.38%
nmt_utils.cpp                        120                89    25.83%           8                 3    62.50%         180               134    25.56%          78                63    19.23%
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                               1586               601    62.11%         140                25    82.14%        3495               902    74.19%        1009               506    49.85%

[gianni-cor]

/review

[github-actions]

Tier-based Approval Status

**PR Tier:** TIER1

**Current Status:** ❌ PENDING

**Requirements:**
- 1 Team Member approval ❌ (0/1)
- 1 Team Lead OR Management approval ✅ (1/1)



---
*This comment is automatically updated when reviews change.*