feat: publish backend operation and supervision contracts

[Brad-Edwards]

Summary

Publish an optional backend operation protocol that binds execution and supervision to the exact admitted context. Backend owners can report refusal, partial effects and uncertain completion while RAE retains authorization, scenario execution and terminal publication.

Requirement UIDs

• API-402

Related Issues

Refs #1360

ADR Impact

• ADR-104
• ADR-113

Changes

• Add four versioned carrier schemas, Python models, contextual validators and an optional backend profile/protocol.
• Publish executable acceptance, refusal, cancellation-race, partial-cancellation, duplicate and reconciliation examples.
• Document provider duties and migration limits; preserve existing runtime profiles and legacy receipt/status/store formats.
• Reconcile API-402 traceability and its existing control-plane governance mapping.

Test Plan

• Unit tests pass
• Integration tests pass if applicable
• Full completion suite required in CI before merge
• No coverage regression

74 operation-contract tests pass after the review fix. The earlier 201-test targeted lifecycle/profile/facade run passed. Generated-schema parity, publication hashes, corpus, file-local policy and requirement governance passed. Full verification runs in CI.

Ground Control Checks

• Repository policy checks required in CI before merge
• Pre-push Codex review completed; all findings fixed or dispositioned

Traceability

• IMPLEMENTS: API-402: backend_operation.py, backend_operation_response.py, backend_operation_validation.py and operation_supervision.py
• TESTS: API-402: test_issue_1360_backend_operations.py and test_issue_1360_operation_rejections.py

Checklist

• Code follows the project's coding standards
• Changelog: owned by Release Please (generated from the Conventional Commit PR title; no per-PR fragment)
• Architectural docs updated if stack, package structure, or key behaviors changed

Documentation

Updated: see diff.

[Brad-Edwards]

Ground Control delivery — this pull request delivers issue #1360; Phase E runs on merge.

[Brad-Edwards]

Ground Control delivery — this pull request delivers issue #1360; Phase E runs on merge.

[Brad-Edwards]

Ground Control delivery — this pull request delivers issue #1360; Phase E runs on merge.