feat: Add VEX compact fixture and implement offline verifier for Findings Ledger exports

- Introduced a new VEX compact fixture for testing purposes.
- Implemented `verify_export.py` script to validate Findings Ledger exports, ensuring deterministic ordering and applying redaction manifests.
- Added a lightweight stub `HarnessRunner` for unit tests to validate ledger hashing expectations.
- Documented tasks related to the Mirror Creator.
- Created models for entropy signals and implemented the `EntropyPenaltyCalculator` to compute penalties based on scanner outputs.
- Developed unit tests for `EntropyPenaltyCalculator` to ensure correct penalty calculations and handling of edge cases.
- Added tests for symbol ID normalization in the reachability scanner.
- Enhanced console status service with comprehensive unit tests for connection handling and error recovery.
- Included Cosign tool version 2.6.0 with checksums for various platforms.

src/Findings/StellaOps.Findings.Ledger/TASKS.md

@@ -13,3 +13,4 @@ Status changes must be mirrored in `docs/implplan/SPRINT_0120_0000_0001_policy_r
 | Task ID | Status | Notes | Updated (UTC) |
 | --- | --- | --- | --- |
 | LEDGER-OBS-54-001 | DONE | Implemented `/v1/ledger/attestations` with deterministic paging, filter hash guard, and schema/OpenAPI updates. | 2025-11-22 |
+| LEDGER-GAPS-121-009 | DONE | FL1–FL10 remediation: schema catalog + export canonicals, Merkle/external anchor policy, tenant isolation/redaction manifest, offline verifier + checksum guard, golden fixtures, backpressure metrics. | 2025-12-02 |