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/excititor/schemas/vex-chunk-api.yaml

@@ -0,0 +1,82 @@
+openapi: 3.1.0
+info:
+  title: StellaOps Excititor Chunk API
+  version: "0.1.0"
+  description: |
+    Frozen for Sprint 110 (EXCITITOR-AIAI-31-002). Aligns with Evidence Locker attestation contract v1.
+servers:
+  - url: https://excitor.local
+paths:
+  /vex/evidence/chunks:
+    post:
+      summary: Submit VEX evidence chunk (aggregation-only)
+      requestBody:
+        required: true
+        content:
+          application/x-ndjson:
+            schema:
+              $ref: '#/components/schemas/VexChunk'
+      responses:
+        '202':
+          description: Accepted for processing
+          content:
+            application/json:
+              schema:
+                type: object
+                required: [chunk_digest, queue_id]
+                properties:
+                  chunk_digest:
+                    type: string
+                    description: sha256 of canonical chunk JSON
+                  queue_id:
+                    type: string
+                    description: Background job identifier
+        '400':
+          description: Validation error
+components:
+  schemas:
+    VexChunk:
+      type: object
+      required: [chunk_id, tenant, source, schema, items, provenance]
+      properties:
+        chunk_id:
+          type: string
+          format: uuid
+        tenant:
+          type: string
+        source:
+          type: string
+          description: feed id (e.g., ghsa, nvd)
+        schema:
+          type: string
+          enum: [stellaops.vex.chunk.v1]
+        items:
+          type: array
+          items:
+            type: object
+            required: [advisory_id, status, purl]
+            properties:
+              advisory_id:
+                type: string
+              status:
+                type: string
+                enum: [affected, unaffected, under_investigation, fixed, unknown]
+              purl:
+                type: string
+              justification:
+                type: string
+              last_observed:
+                type: string
+                format: date-time
+        provenance:
+          type: object
+          required: [fetched_at, artifact_sha]
+          properties:
+            fetched_at:
+              type: string
+              format: date-time
+            artifact_sha:
+              type: string
+            signature:
+              type: object
+              nullable: true