feat(orch): api_delegate MCP tool for HTTP-only providers (xAI Grok)

[cnighswonger]

Summary

Adds an api_delegate MCP tool for HTTP-only LLM providers (no local CLI binary), with xAI Grok as the initial provider. Sits alongside the existing cli_delegate so callers can choose either pathway without changing how results are consumed downstream.

cli_status and cli_probe extended to surface API providers alongside CLI providers; each row carries a new kind field ("cli-binary" vs "http-api") so callers can distinguish.

Motivation

Grok is useful as a sometimes-adversarial reviewer in writing workflows. Wrapping it as a fake CLI shim felt like more friction than value (the xAI API is one HTTP endpoint), so this adds a sibling path that treats HTTP-only providers natively. Future providers (OpenAI direct API, Anthropic direct API) drop into the same PROVIDERS dict — endpoint, default model, key resolver, response extractor.

Design

New module: src/llm_relay/orch/api_executor.py

Stdlib-only (urllib + ssl). Mirrors executor.py's shape so MCP/DB/history machinery treats both paths uniformly.

• PROVIDERS dict keyed by short name; each entry has provider_id, endpoint, default_model, key_resolver callable, extract callable, auth_method, api_key_name.
• execute_api(provider, prompt, model=None, system=None, timeout=120, max_tokens=4000, temperature=0.3) returns DelegationResult shaped identically to CLI execution — exit_code=0 on success per the CLI-executor convention (proxy/composition.py:814 checks exit_code == 0).
• xAI/Grok key resolution: XAI_API_KEY_PATH (file) → ~/.llm-relay/grok.key → ~/grok.key (legacy) → XAI_API_KEY env var.
• Key file permission gating: requires POSIX mode 0o600 or stricter; loose-permission files silently skipped with debug log. Windows exempt (st_mode bits don't carry equivalent meaning).
• HTTPS scheme guard: refuses non-HTTPS endpoints before urlopen() is reached. PROVIDERS dict is in-tree, so this is defense against future misedits rather than untrusted input.
• Provider-supplied hooks (key_resolver, extract) wrapped in try/except so a misbehaving provider returns a clean DelegationResult instead of bubbling.

New MCP tool: api_delegate

api_delegate(provider, prompt, model="", system="", timeout=120, max_tokens=4000)

• Logs to delegation DB with strategy="api-direct".
• Respects LLM_RELAY_HISTORY=1 for session-history capture.
• Returns the same JSON envelope as cli_delegate plus model_used.

Extended: cli_status and cli_probe

Both surface API providers in addition to CLI providers. New kind field distinguishes:

{"cli_id": "claude-code", "kind": "cli-binary", ...}
{"cli_id": "xai-grok",    "kind": "http-api",   ...}

Tests

24 new in tests/test_orch/test_api_executor.py covering:

• Provider listing + status (with and without a usable key)
• All error paths: unknown provider, no key, HTTP error, transport error, non-JSON response, empty choices, key_resolver() raising, extract() raising
• Success path with mocked urlopen — confirms model + system + auth header construction
• Key resolution precedence (file path > legacy ~/grok.key > env var)
• Permission gating (rejects 0o644 and 0o640, accepts 0o600)
• HTTPS scheme guard fires before urlopen() is reached
• Payload-failure exit codes use 502 sentinel, not the HTTP status code

TestCliStatus tests in tests/test_mcp/test_server.py updated to mock the API-provider surface so they stay focused on CLI behavior; added a new test_includes_api_providers asserting cross-surface integration.

Full suite: 618 pass + 1 pre-existing failure (test_codex_basic, env-sensitive, unrelated to this change).

Review history

This change went through Codex strict-technical review, an open-ended adversarial Grok review (via the new tool itself, dogfooding the round-trip), and a final Codex pass. Each round caught real bugs. Of note: the success-path exit_code was the one place Grok's review pointed at the right gap but suggested an incomplete fix (HTTP status code as exit code); Codex's second pass caught that the success path needed to return 0 per the existing CLI-executor convention. The disagreement is the reason this PR exists in its current shape.

Provider boundary

API keys are read at request time (not module load), so rotating ~/.llm-relay/grok.key requires no daemon restart. The PR does not introduce any always-on outbound calls — the new path is invoked only when a caller explicitly delegates to it.

Test plan

• pytest tests/test_orch/test_api_executor.py — 24 pass
• pytest tests/test_mcp/test_server.py — all green
• pytest full suite — 618 pass (the one pre-existing failure is unrelated and reproduces on main without this PR)
• End-to-end: with a valid xAI key at ~/.llm-relay/grok.key (mode 0600), restart daemon, call api_delegate(provider="grok", prompt="reply WORKING") via MCP — should round-trip in ~1-2s with success=true, cli_id="xai-grok", exit_code=0.

— AI Team Lead