fix(runtime): add snapshot revision compare-and-swap

[Brad-Edwards]

Plain-Language Summary

• Context: Runtime control-plane mutations can originate from concurrent writers that share one durable snapshot store.
• Problem: A writer could persist an update derived from an older snapshot and silently overwrite newer snapshot, operation, or audit state.
• Fix: Add provider-neutral observed revisions, atomic compare-and-swap commits, revision-pinned reads, and regression coverage for stale-writer isolation.

Issue Tracking

Closes #1180

Verification

• Ground Control completion suite: passed.
• Repository policy gate: passed.
• Focused snapshot-CAS and participant-flow regression suites: 47 tests passed.
• Pre-push code review findings were repaired; independent test-quality review passed cleanly.

Summary

Add provider-neutral snapshot revisions and compare-and-swap persistence so concurrent control-plane writers cannot silently overwrite newer durable state.

Requirement UIDs

• (none — bug/refactor/maintenance run; see Traceability section below)

Related Issues

Closes #1180

ADR Impact

• ADR-021
• ADR-036
• ADR-104

Changes

• Require observed snapshot revisions for every snapshot-bearing commit and reject stale writers atomically across in-memory, SQLite, and compatible custom stores.
• Pin derived reads and participant projections to one observed snapshot revision while keeping provider revisions out of portable snapshot metadata.
• Demote runtime caches to rebuildable projections and expose the observed revision on snapshot-derived HTTP responses.
• Migrate durable records to revision-aware state and document the concurrency, compatibility, and cache boundaries.
• Migration reminder: this change includes a migration — verify the repo's migration/version references and run its migration checks per the repository's migration policy.

Test Plan

• Unit tests pass
• Integration tests pass if applicable
• Configured completion command passes
• No coverage regression

Ground Control completion and repository-policy gates passed after the final review fixes; focused snapshot-CAS and participant-flow regression suites also passed (47 tests).

Ground Control Checks

• Configured repository policy command passes
• Pre-push code review and test-quality review completed; all findings fixed or dispositioned

Traceability

• IMPLEMENTS: API-404 ← implementations/python/packages/raes_runtime/control_plane_store_revision.py, API-404 ← implementations/python/packages/raes_runtime/control_plane_store_local_snapshot.py, API-404 ← implementations/python/packages/raes_runtime/control_plane_durability.py, API-404 ← implementations/python/packages/raes_runtime/control_plane_api/_responses.py
• TESTS: API-404 ← implementations/python/tests/test_issue_1180_snapshot_revision_cas.py, API-404 ← implementations/python/tests/test_run_319_participant_flow_policy.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.