Python Service: OpenAPI Source-of-Truth Discipline

Schema-derived client generation must have a clear source of truth.

Rationale:
- Unclear ownership of generated artifacts causes drift and non-reproducible builds.

Scope:
- PR review policy for Python services that generate API client code from OpenAPI/schema inputs.

Trigger:
- A PR adds or changes schema snapshot/reduction/codegen inputs, generated client policy, or generation scripts.

Approval checks:
1) Committed source-of-truth inputs are explicit (schema/snapshot + transformation/codegen config).
2) Generated artifact policy is explicit and consistent:
   - generated code committed intentionally and maintained, or
   - generated code treated as ephemeral and reproducibly generated.
3) Runtime/quality entrypoints enforce generated-client freshness before use.

Evidence:
- Diff shows source-of-truth inputs and generation policy alignment (`.gitignore`, scripts, docs, CI).

Exception path:
- Allow deviation only when all are true:
1) PR description includes `Policy Exception: python-openapi-source-of-truth`.
2) PR explains why default artifact policy is unsuitable.
3) PR documents replacement reproducibility controls.

Decision:
- Return NOT APPROVED when trigger is met and source-of-truth/freshness controls are unclear without a valid exception.