[Ops][Slice] CI + policy evidence enforcement

[Prekzursil]

Parent: #39

Scope

Enforce reliability policy in CI and PR workflows.

Acceptance Criteria

• CI validates repro-bundle fixture sample in addition to launch-context fixture.
• policy-contract.yml checks AGENTS/templates contracts.
• PR evidence enforcement fails when runtime/tooling/tests changes lack reliability evidence fields.
• PR template includes affected profile + reason-code evidence sections.

Evidence

• CI run with build-test + policy-contract checks green.