Implement ledger metrics for observability and add tests for Ruby packages endpoints

- Added `LedgerMetrics` class to record write latency and total events for ledger operations.
- Created comprehensive tests for Ruby packages endpoints, covering scenarios for missing inventory, successful retrieval, and identifier handling.
- Introduced `TestSurfaceSecretsScope` for managing environment variables during tests.
- Developed `ProvenanceMongoExtensions` for attaching DSSE provenance and trust information to event documents.
- Implemented `EventProvenanceWriter` and `EventWriter` classes for managing event provenance in MongoDB.
- Established MongoDB indexes for efficient querying of events based on provenance and trust.
- Added models and JSON parsing logic for DSSE provenance and trust information.

docs/modules/findings-ledger/replay-harness.md

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+# Findings Ledger Replay & Determinism Harness (LEDGER-29-008)
+
+> **Audience:** Findings Ledger Guild · QA Guild · Policy Guild  
+> **Purpose:** Define the reproducible harness for 5 M findings/tenant replay tests and determinism validation required by LEDGER-29-008.
+
+## 1. Goals
+- Reproduce ledger + projection state from canonical event fixtures with byte-for-byte determinism.
+- Stress test writer/projector throughput at ≥5 M findings per tenant, capturing CPU/memory/latency profiles.
+- Produce signed reports (DSSE) that CI and auditors can review before shipping.
+
+## 2. Architecture
+
+```
+Fixtures (.ndjson) → Harness Runner → Ledger Writer API → Postgres Ledger DB
+                                     ↘ Projector (same DB) ↘ Metrics snapshot
+```
+
+- **Fixtures:** `fixtures/ledger/*.ndjson`, sorted by `sequence_no`, containing canonical JSON envelopes with precomputed hashes.
+- **Runner:** `tools/LedgerReplayHarness` (console app) feeds events, waits for projector catch-up, and verifies projection hashes.
+- **Validation:** After replay, the runner re-reads ledger/projection tables, recomputes hashes, and compares to fixture expectations.
+- **Reporting:** Generates `harness-report.json` with metrics (latency histogram, insertion throughput, projection lag) plus a DSSE signature.
+
+## 3. CLI usage
+
+```bash
+dotnet run --project tools/LedgerReplayHarness \
+  -- --fixture fixtures/ledger/tenant-a.ndjson \
+     --connection "Host=postgres;Username=stellaops;Password=***;Database=findings_ledger" \
+     --tenant tenant-a \
+     --maxParallel 8 \
+     --report out/harness/tenant-a-report.json
+```
+
+Options:
+
+| Option | Description |
+| --- | --- |
+| `--fixture` | Path to NDJSON file (supports multiple). |
+| `--connection` | Postgres connection string (writer + projector share). |
+| `--tenant` | Tenant identifier; harness ensures partitions exist. |
+| `--maxParallel` | Batch concurrency (default 4). |
+| `--report` | Output path for report JSON; `.sig` generated alongside. |
+| `--metrics-endpoint` | Optional Prometheus scrape URI for live metrics snapshot. |
+
+## 4. Verification steps
+
+1. **Hash validation:** Recompute `event_hash` for each appended event and ensure matches fixture.
+2. **Sequence integrity:** Confirm gapless sequences per chain; harness aborts on mismatch.
+3. **Projection determinism:** Compare projector-derived `cycle_hash` with expected value from fixture metadata.
+4. **Performance:** Capture P50/P95 latencies for `ledger_write_latency_seconds` and ensure targets (<120 ms P95) met.
+5. **Resource usage:** Sample CPU/memory via `dotnet-counters` or `kubectl top` and store in report.
+6. **Merkle root check:** Rebuild Merkle tree from events and ensure root equals database `ledger_merkle_roots` entry.
+
+## 5. Output report schema
+
+```json
+{
+  "tenant": "tenant-a",
+  "fixtures": ["fixtures/ledger/tenant-a.ndjson"],
+  "eventsWritten": 5123456,
+  "durationSeconds": 1422.4,
+  "latencyP95Ms": 108.3,
+  "projectionLagMaxSeconds": 18.2,
+  "cpuPercentMax": 72.5,
+  "memoryMbMax": 3580,
+  "merkleRoot": "3f1a…",
+  "status": "pass",
+  "timestamp": "2025-11-13T11:45:00Z"
+}
+```
+
+The harness writes `harness-report.json` plus `harness-report.json.sig` (DSSE) and `metrics-snapshot.prom` for archival.
+
+## 6. CI integration
+- New pipeline job `ledger-replay-harness` runs nightly with reduced dataset (1 M findings) to detect regressions quickly.
+- Full 5 M run executes weekly and before releases; artifacts uploaded to `out/qa/findings-ledger/`.
+- Gates: merge blocked if harness `status != pass` or latencies exceed thresholds.
+
+## 7. Air-gapped execution
+- Include fixtures + harness binaries inside Offline Kit under `offline/ledger/replay/`.
+- Provide `run-harness.sh` script that sets env vars, executes runner, and exports reports.
+- Operators attach signed reports to audit trails, verifying hashed fixtures before import.
+
+---
+
+*Draft prepared 2025-11-13 for LEDGER-29-008. Update when CLI options or thresholds change.*