Add new features and tests for AirGap and Time modules

- Introduced `SbomService` tasks documentation.
- Updated `StellaOps.sln` to include new projects: `StellaOps.AirGap.Time` and `StellaOps.AirGap.Importer`.
- Added unit tests for `BundleImportPlanner`, `DsseVerifier`, `ImportValidator`, and other components in the `StellaOps.AirGap.Importer.Tests` namespace.
- Implemented `InMemoryBundleRepositories` for testing bundle catalog and item repositories.
- Created `MerkleRootCalculator`, `RootRotationPolicy`, and `TufMetadataValidator` tests.
- Developed `StalenessCalculator` and `TimeAnchorLoader` tests in the `StellaOps.AirGap.Time.Tests` namespace.
- Added `fetch-sbomservice-deps.sh` script for offline dependency fetching.

docs/modules/evidence-locker/attestation-contract.md

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+# Evidence Locker Attestation Contract (v1 · frozen 2025-11-20)
+
+Scope: Evidence Bundle v1 produced by Evidence Locker and consumed by Concelier, Excititor, Export Center, CLI, and Policy Engine.
+
+## Predicates & subjects
+- **Subject**: OCI manifest digest (`sha256:<digest>`) of the bundle, plus optional replay pack digest.
+- **Predicates (DSSE/In-Toto)**
+  - `stellaops.evidence.bundle.v1`: declares bundle layout (manifests, CAS paths, replay log offsets).
+  - `stellaops.evidence.transparency.v1`: optional Rekor log inclusion proof (UUID, log index, root hash at inclusion).
+  - `stellaops.evidence.integrity.v1`: hashes for each payload (SBOMs, VEX, policy packs, telemetry snapshots), keyed by logical path.
+
+## Required claim set
+- `bundle_id` (UUID v4)
+- `produced_at` (UTC ISO-8601)
+- `producer` (`evidence-locker:<region>`)
+- `subject_digest` (OCI digest string)
+- `hashes` (map: logical path → sha256)
+- `sbom` (array of SPDX/CycloneDX digests and mediaTypes)
+- `vex` (array of VEX doc digests and schema versions)
+- `replay_manifest` (optional; digest + sequence number)
+- `transparency` (optional; Rekor UUID, logIndex, rootHash)
+- `signing_profile` (`sovereign-default` | `fips` | `gost` | `pq-experimental`)
+
+## Bundling & signing rules
+- DSSE envelope using the module’s configured crypto provider; keys must be short-lived (<24h) and recorded in provider registry.
+- Hash list and subject digest MUST match the on-disk CAS objects; deterministic sort by logical path.
+- Rekor entry is optional; when absent, set `transparency=null` and add `transparency_reason="offline"` to provenance note.
+
+## Verification plan
+- Verify DSSE signature against provider registry (per profile) and check key expiry.
+- Recompute sha256 for every CAS object; fail if any mismatch.
+- If `transparency` present, verify inclusion proof against bundled Rekor root; fail closed on mismatch.
+- Emit verification report JSON and store beside bundle as `verify.json` (deterministic key order).
+
+## Fixtures
+- Sample bundle + report: `docs/samples/evidence-locker/bundle-v1-sample.tar.gz` (sha256 TBD at publish time).
+- Sample attestation envelope: `docs/samples/evidence-locker/attestation-v1-sample.json`.
+
+## Ownership
+- Primary: Evidence Locker Guild.
+- Reviewers: Concelier Core Guild, Excititor Guild, Export Center Guild, Policy Guild.
+
+This contract is authoritative for Sprint 110 and blocks CONCELIER-ATTEST-73-001/002 and EXCITITOR-ATTEST-01-003/73-001/73-002.