feat: zero-config OpenRouter for the plan() pipeline

[AbirAbbas]

Summary

The OpenRouter auto-selection added in #88 only reaches the build/execute path (ExecutionConfig/BuildConfig use default_factory=_default_runtime). The plan pipeline and its per-role model args hardcoded ai_provider="claude" / model="sonnet", so on an OpenRouter-only deployment:

af call swe-planner.plan '{"goal":"...","repo_path":"..."}'

tried Claude and failed — you had to pass ai_provider=open_code + model=openrouter/... on every call. (Discovered while smoke-testing an OpenRouter-only install: run_product_manager only succeeded once those were passed explicitly.)

Change

plan()'s ai_provider and the five *_model arguments now default to None and resolve from the environment, mirroring build/execute:

• ai_provider → _default_runtime() — honors SWE_DEFAULT_RUNTIME; auto-selects open_code when only an OpenRouter key is present, else claude_code.
• *_model → new _default_planning_model():
  1. deployer env cascade SWE_DEFAULT_MODEL → AI_MODEL → HARNESS_MODEL
  2. the OpenRouter default (openrouter/deepseek/deepseek-v4-flash) when OpenRouter-only
  3. "sonnet" otherwise (historical default)

Explicit arguments always win. Claude users see no behavior change — claude_code maps to the same claude-code harness the old "claude" did.

Validation contract

• OpenRouter-only env, no args → sub-reasoners get ai_provider="open_code", model="openrouter/deepseek/deepseek-v4-flash".
• Anthropic key present → ai_provider="claude_code", model="sonnet" (unchanged).
• SWE_DEFAULT_MODEL (or AI_MODEL/HARNESS_MODEL) set → that model wins, on either path.
• Explicit ai_provider/*_model args → always honored over the env.

Tests

• TestDefaultPlanningModel — _default_planning_model() across the env matrix (claude / none / openrouter-only / SWE_DEFAULT_MODEL / AI_MODEL cascade).
• Four plan()-wiring tests asserting the resolved ai_provider/model reach the first sub-reasoner call.

make check (pytest test_planner_pipeline.py + test_model_config.py = 68 passed incl. new; compileall) green.

Note: pairs with #89 (honor the control-plane PORT) — both needed for a clean af install → af run → af call on an OpenRouter-only box.

🤖 Generated with Claude Code