feat: Add DigestUpsertRequest and LockEntity models

- Introduced DigestUpsertRequest for handling digest upsert requests with properties like ChannelId, Recipient, DigestKey, Events, and CollectUntil.
- Created LockEntity to represent a lightweight distributed lock entry with properties such as Id, TenantId, Resource, Owner, ExpiresAt, and CreatedAt.

feat: Implement ILockRepository interface and LockRepository class

- Defined ILockRepository interface with methods for acquiring and releasing locks.
- Implemented LockRepository class with methods to try acquiring a lock and releasing it, using SQL for upsert operations.

feat: Add SurfaceManifestPointer record for manifest pointers

- Introduced SurfaceManifestPointer to represent a minimal pointer to a Surface.FS manifest associated with an image digest.

feat: Create PolicySimulationInputLock and related validation logic

- Added PolicySimulationInputLock record to describe policy simulation inputs and expected digests.
- Implemented validation logic for policy simulation inputs, including checks for digest drift and shadow mode requirements.

test: Add unit tests for ReplayVerificationService and ReplayVerifier

- Created ReplayVerificationServiceTests to validate the behavior of the ReplayVerificationService under various scenarios.
- Developed ReplayVerifierTests to ensure the correctness of the ReplayVerifier logic.

test: Implement PolicySimulationInputLockValidatorTests

- Added tests for PolicySimulationInputLockValidator to verify the validation logic against expected inputs and conditions.

chore: Add cosign key example and signing scripts

- Included a placeholder cosign key example for development purposes.
- Added a script for signing Signals artifacts using cosign with support for both v2 and v3.

chore: Create script for uploading evidence to the evidence locker

- Developed a script to upload evidence to the evidence locker, ensuring required environment variables are set.

docs/modules/policy/contracts/spine-versioning-plan.md

@@ -0,0 +1,64 @@
+# SBOM/VEX Spine Versioning Plan (SP1)
+
+## Purpose
+Establish versioned spine API/DTO schemas with migration rules, determinism guarantees, and DSSE-backed manifests, covering SP1–SP10 gaps from the 31-Nov-2025 findings advisory.
+
+## Scope
+- Spine APIs and DTOs shared by Scanner, Policy, Authority, and Graph.
+- Manifest/signing layers for spine bundles (online + offline).
+- Pagination/performance envelopes and Unknowns workflow.
+
+## Deliverables (SP tasks)
+- SP1: Versioned schemas + header/version negotiation rules; deprecation timetable.
+- SP2: Evidence requirements per predicate/edge (reachability proof, package identity, build metadata) with MUST/SHOULD fields.
+- SP3: Unknowns registry contract (states, SLA, surfacing rules, expiry/decay).
+- SP4: DSSE-signed spine manifest listing hashes for all artifacts; Rekor/mirror policy hooks.
+- SP5: Deterministic diff rules + fixtures (ordered deltas, canonical sorting, hash expectations).
+- SP6: Feed snapshot freshness/staleness thresholds and validation steps.
+- SP7: Stage-by-stage DSSE requirements, Rekor/mirror policy matrices (online/offline).
+- SP8: Policy lattice version field and embedding rules in spine objects.
+- SP9: Pagination/ordering/perf budgets (stable sort keys, default page size limits, deterministic cursors).
+- SP10: Crosswalk mappings SBOM ↔ VEX ↔ graph ↔ policy (table + sample payloads).
+
+## Migration & Determinism
+- Version headers and DTO version fields must be required; rejects if missing or downgraded without declared adapter.
+- Canonical JSON ordering for manifests; hashes computed over canonical form (UTF-8, no BOM).
+- Pagination uses deterministic primary/secondary sort keys; cursors are opaque, HMAC-free, reproducible from sort key + last id.
+
+### Versioning mechanics (v0.1)
+- Header: `X-Spine-Version: v1` (required). DTO field mirror: `schemaVersion` (string, semver).
+- Deprecation window: N-1 supported for 90 days; adapters required to downgrade v2→v1 (CSV in `docs/modules/policy/fixtures/spine-adapters/`).
+- Hashing: canonical JSON, sorted properties, UTF-8 no BOM, normalized decimals (4dp), timestamps UTC ISO-8601.
+
+### Evidence minima per edge (SP2, draft)
+- `reachability`: state, confidence, score, method, evidenceRef (hash or URI), runtimeEvidence flag (bool).
+- `package_identity`: purl, name, version, supplier, hashes[] (at least SHA256).
+- `build_metadata`: buildId, sourceRepo, sourceRef, buildInvokerHash, provenanceHash (DSSE).
+
+### Unknowns workflow (SP3, draft)
+- States: `unknown`, `under_review`, `resolved`, `expired`.
+- SLA: auto-review escalation after 7 days; decay to `expired` at 30 days unless refreshed.
+- Surfacing: APIs must include `unknowns.count` and list endpoint with deterministic pagination; optional policy lattice flag to penalize unknowns.
+
+### Signing (SP4/SP7)
+- Manifest structure: list of artifacts (type, id, hash, version, uri), signed using DSSE/ED25519 by default; Rekor optional online, mirrored checkpoints offline.
+- Stage policy: compile → ingest → materialize → export; each stage produces DSSE, carries prior stage hash for chain-of-custody.
+
+### Pagination/perf budgets (SP9)
+- Default page size 200; max 500; stable sort: tenant asc, subjectPurl asc, advisoryId asc, createdAt asc.
+- Cursors: base64-encoded tuple of sort keys; must round-trip deterministically.
+
+### Crosswalk (SP10)
+- Provide table mapping: SBOM component ↔ spine node ↔ graph node ↔ policy evaluation input; include sample payloads in `docs/modules/policy/fixtures/spine-crosswalk/`.
+
+## Signing & Offline
+- DSSE envelope mandatory for spine manifest; Rekor entry optional online, mirrored checkpoints for offline kits.
+- Mirror bundles carry: manifest hash list, time-anchor digest, toolkit hashes, version map for adapters.
+
+## Open Items
+- Finalize evidence minima per predicate with Signals/Reachability guild once runtime schema lands.
+- Confirm lattice versioning alignment with policy engine release cadence.
+
+## Links
+- Sprint: `docs/implplan/SPRINT_0186_0001_0001_record_deterministic_execution.md` (SP1–SP10)
+- Advisory: `docs/product-advisories/31-Nov-2025 FINDINGS.md`