Add executor-scoped replay cache aligned with Codex HOME replay:
Scope, observe SSE/non-stream responses, store normalized thought_signature
and function_call_part items, apply on the next streamGenerateContent
request, and invalidate on invalid signature responses.
Gemini/flash/agent models use HOME replay; native per-part signature
replay is not wired on upstream/dev. Wire non-stream and stream paths
in antigravity_executor and purge expired entries from signature_cache.
Includes unit tests and HOME-provider-replay documentation.
- Updated Antigravity Credits fallback to handle KV store unavailability as a service error.
- Enhanced signature caching mechanisms with request-time KV access and sliding expiration.
- Added and improved tests for KV client interactions, including error handling and expiration behaviors.
- Introduced `CacheSignatureBestEffort` for non-critical signature caching and clarified function flows with required context.
- Ensured consistent error reporting for missing or unavailable KV stores in various scenarios.
- Replaced direct `homekv` calls with injectable KV client interfaces for `antigravity` and `codex_reasoning_replay` modules.
- Improved error reporting and handling for KV operations, including `KVGet`, `KVSet`, `KVDel`, and `KVExpire`.
- Introduced dedicated fake KV clients for expanded and granular test coverage.
- Added new unit tests to validate KV client behaviors and error scenarios, ensuring robustness and sliding expiration functionality.
Improve the cache eviction routine to sort entries by timestamp using the standard library sort routine (stable, clearer and faster than the prior manual selection/bubble logic), and remove a redundant request-derived session ID helper in favor of the centralized session ID function. Also drop now-unused crypto/encoding imports.
This yields clearer, more maintainable eviction logic and removes duplicated/unused code and imports to reduce surface area and potential inconsistencies.
