Implement Advisory Canonicalization and Backfill Migration

- Added AdvisoryCanonicalizer for canonicalizing advisory identifiers.
- Created EnsureAdvisoryCanonicalKeyBackfillMigration to populate advisory_key and links in advisory_raw documents.
- Introduced FileSurfaceManifestStore for managing surface manifests with file system backing.
- Developed ISurfaceManifestReader and ISurfaceManifestWriter interfaces for reading and writing manifests.
- Implemented SurfaceManifestPathBuilder for constructing paths and URIs for surface manifests.
- Added tests for FileSurfaceManifestStore to ensure correct functionality and deterministic behavior.
- Updated documentation for new features and migration steps.

src/Scheduler/__Libraries/StellaOps.Scheduler.Worker/TASKS.md

@@ -3,6 +3,7 @@
 | ID | Status | Owner(s) | Depends on | Description | Exit Criteria |
 |----|--------|----------|------------|-------------|---------------|
 | SCHED-SURFACE-01 | TODO | Scheduler Worker Guild | SURFACE-FS-02, SCANNER-SURFACE-02 | Evaluate Surface.FS pointers when planning delta scans to avoid redundant work and prioritise drift-triggered assets. | Planner reads Surface.FS manifests; regression tests cover cache hits/misses; documentation updated. |
+| SCHED-SURFACE-02 | TODO | Scheduler Worker Guild, Surface FS Guild | SURFACE-FS-02, SCHED-SURFACE-01 | Integrate Surface manifest reader to prefetch CAS manifests before scheduling reruns and persist pointer metadata alongside run plans. See `docs/modules/scanner/design/surface-fs-consumers.md` §3 for checklist. | Prefetch pipeline prevents redundant scans; scheduler persists manifest URIs/digests; integration tests cover cache hit/miss fallbacks and telemetry wiring. |
 
 > 2025-10-27: Impact targeting sanitizes selector-constrained results, dedupes digests, and documents shard planning in `docs/SCHED-WORKER-16-202-IMPACT-TARGETING.md`.