Add unit and integration tests for VexCandidateEmitter and SmartDiff repositories

- Implemented comprehensive unit tests for VexCandidateEmitter to validate candidate emission logic based on various scenarios including absent and present APIs, confidence thresholds, and rate limiting.
- Added integration tests for SmartDiff PostgreSQL repositories, covering snapshot storage and retrieval, candidate storage, and material risk change handling.
- Ensured tests validate correct behavior for storing, retrieving, and querying snapshots and candidates, including edge cases and expected outcomes.

docs/24_OFFLINE_KIT.md

@@ -305,10 +305,10 @@ The Offline Kit carries the same helper scripts under `scripts/`:
 
 1. **Duplicate audit:** run
    ```bash
-   mongo concelier ops/devops/scripts/check-advisory-raw-duplicates.js --eval 'var LIMIT=200;'
+   psql -d concelier -f ops/devops/scripts/check-advisory-raw-duplicates.sql -v LIMIT=200
    ```
    to verify no `(vendor, upstream_id, content_hash, tenant)` conflicts remain before enabling the idempotency index.
-2. **Apply validators:** execute `mongo concelier ops/devops/scripts/apply-aoc-validators.js` (and the Excititor equivalent) with `validationLevel: "moderate"` in maintenance mode.
+2. **Apply validators:** execute `psql -d concelier -f ops/devops/scripts/apply-aoc-validators.sql` (and the Excititor equivalent) with `validationLevel: "moderate"` in maintenance mode.
 3. **Restart Concelier** so migrations `20251028_advisory_raw_idempotency_index` and `20251028_advisory_supersedes_backfill` run automatically. After the restart:
    - Confirm `db.advisory` resolves to a view on `advisory_backup_20251028`.
    - Spot-check a few `advisory_raw` entries to ensure `supersedes` chains are populated deterministically.