tech-debt: 重复的 BatchedEngine 实现 (engine/batched/ vs engines/batched.py) 需合并

[dahai80]

现状

竞品审计报告 (fusion-mlx_vs_*.md) 一致指出存在两套 BatchedEngine 实现：

• fusion_mlx/engine/batched/__init__.py (357 行) — class BatchedEngine(BaseEngine)，独立实现，含 _mtp_dispatch.py
• fusion_mlx/engines/batched.py (1157 行) — class BatchedEngine(BaseEngine)，生产实现（server.py + engine_pool.py 用这个）

证据

$ grep -rln 'engines.batched' fusion_mlx/   # 生产导入者
fusion_mlx/server.py
fusion_mlx/pool/engine_pool.py
fusion_mlx/pool/engine/dflash.py

$ grep -rln 'engine.batched' fusion_mlx/    # 生产代码零导入者
# (空)

$ grep -rln 'engine.batched' tests/         # 仅测试依赖
tests/unit/test_no_mllm_flag.py
tests/unit/test_embeddings_timeout_admission.py
tests/unit/test_batching.py
tests/unit/test_disconnect_guard_aborts_scheduler.py
tests/unit/test_batched_engine_output_router.py
# ... 20+ 测试文件

风险

engine/batched/ 子包在生产代码中零导入者，但被 20+ 测试文件直接 import。两套实现分叉，维护时易改错一份，是架构冗余的典型信号（见三份竞品报告的「关键差距与风险」章节）。

复杂度

不能简单删除 engine/batched/ —— 20+ 测试依赖它，且这些测试多数在 debt_modules.txt 隔离名单内（已知失败）。清理需：

1. 确认 engine/batched/ 是否为旧入口/shim（engine/__init__.py 仍 from . import batched）
2. 决定单一权威实现（生产用 engines/batched.py）
3. 将依赖 engine.batched 的测试迁移到 engines.batched，或确认这些测试本身已是死测试随隔离名单清理

来源

竞品深度对比报告 (~/fusion/audit/fusion-mlx_vs_*.md) 行动项。本 issue 仅记录技术债，不在 GGUF 桥 PR 中一并处理（风险不对等）。

Co-Authored-By: Claude Fable 5 noreply@anthropic.com

[dahai80]

Investigation finding (corrects one premise in the issue)

The issue stated engine/batched/ 子包 has "生产代码零导入者". That's true for the BatchedEngine class but not for the whole package:

• engine/batched/__init__.py::BatchedEngine — ✅ zero production importers (confirmed: server.py, engine_pool.py, engines/__init__.py all use engines.batched.BatchedEngine)
• engine/batched/_mtp_dispatch.py — ❌ IS live: imported by the production engine at engines/batched.py:362 (from ..engine.batched._mtp_dispatch import _apply_mtp_dispatch) and by the active test_mtp_cli_wiring.py suite (58 tests) via the __init__.py re-exports

So the package cannot be deleted wholesale. The surgical fix is to remove only the dead class and keep _mtp_dispatch as a thin shim.

Fix

PR #428 — removes the dead BatchedEngine class (−341 lines), keeps _mtp_dispatch + re-exports. Verified: test_mtp_cli_wiring 57 passed, full collection 8849 tests no import errors.

🤖 Verified by Claude Code