feat: Implement Filesystem and MongoDB provenance writers for PackRun execution context

- Added `FilesystemPackRunProvenanceWriter` to write provenance manifests to the filesystem.
- Introduced `MongoPackRunArtifactReader` to read artifacts from MongoDB.
- Created `MongoPackRunProvenanceWriter` to store provenance manifests in MongoDB.
- Developed unit tests for filesystem and MongoDB provenance writers.
- Established `ITimelineEventStore` and `ITimelineIngestionService` interfaces for timeline event handling.
- Implemented `TimelineIngestionService` to validate and persist timeline events with hashing.
- Created PostgreSQL schema and migration scripts for timeline indexing.
- Added dependency injection support for timeline indexer services.
- Developed tests for timeline ingestion and schema validation.

docs/modules/vex-lens/AGENTS.md

@@ -8,6 +8,7 @@ VEX Lens computes deterministic consensus across conflicting VEX statements whil
 - [Architecture](./architecture.md)
 - [Implementation plan](./implementation_plan.md)
 - [Task board](./TASKS.md)
+- [Observability runbook](./runbooks/observability.md) (offline import friendly)
 
 ## How to get started
 1. Review ./architecture.md for consensus algorithm, trust model, and export contracts.