Degrade OpenAPI action_id collisions instead of crashing the scan

[pengfei-threemoonslab]

Summary

• A valid third-party OpenAPI spec (block/goose, found by the merged-PR miner) crashed agents-shipgate scan with exit 2 / Config error: Duplicate action_surface action_id. The OpenAPI action_id is derived from METHOD + normalized_path only — the operationId is dropped — so two distinct operations whose paths normalize identically (goose ships GET /sessions/{session_id} plus a trailing-slash variant, each with its own operationId) collapse to one action_id and hard-fail the duplicate-id guard.
• Make this fail-soft, matching the symlink-loop (Add the merged-PR history miner + first real run (WS-P) #212) and MCP-as-tools (init: never write a tool source that scan's input adapters reject #214) precedent: a third-party spec must never crash a scan. Collisions now degrade to a source_warning (which routes the release to review_required) while keeping both operations as distinct actions.
• build_action_surface_facts gains an optional warnings sink. When provided (the live scan path), _disambiguate_duplicate_action_ids deterministically resolves collisions: the first operation (by tool_name) keeps the bare id, the rest gain a #<operationId> suffix (ordinal fallback when operationIds also tie), identity_hash is refreshed, and one warning is recorded per collision. Without a sink the legacy ConfigError is preserved, so the redaction path's existing public-only ordinal disambiguator (surface_redaction.py) is untouched.
• The warnings are threaded from Phase 5 (decision.py → _ChecksDecision → sanitization.py) into report.source_warnings, appended last so output stays byte-stable for the common no-collision case (the list is empty there).

Type

• Check or risk-model change
• Input adapter change

Verification

CI is authoritative for python -m ruff check ., python -m compileall -q src tests, and python -m pytest.

Additional local checks run:

• Full pytest suite passes (exit 0); tests/test_adapter_static_only.py static-only invariant holds; ruff check clean on all changed files.
• New network-free regression tests: test_action_surface_disambiguates_openapi_action_id_collisions_fail_soft (unit) and test_openapi_action_id_collision_degrades_instead_of_crashing (full run_scan on the goose-shaped fixture). The existing test_action_surface_rejects_action_id_collisions (no sink → ConfigError) still passes.
• End-to-end CLI on the fixture now returns exit 0 with the disambiguation source_warning and two distinct action_ids, instead of the previous exit 2 / Config error.

Release-readiness notes

• No user-code import added to default scan paths
• No network access added to default scan paths
• New or changed check IDs are documented in docs/checks.md — n/a, no new check IDs
• Report/schema changes are additive or documented in STABILITY.md — no schema change; source_warnings only gains an extra entry in the (previously crashing) collision case

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