feat(crypto): Complete Phase 2 - Configuration-driven crypto architecture with 100% compliance

## Summary

This commit completes Phase 2 of the configuration-driven crypto architecture, achieving
100% crypto compliance by eliminating all hardcoded cryptographic implementations.

## Key Changes

### Phase 1: Plugin Loader Infrastructure
- **Plugin Discovery System**: Created StellaOps.Cryptography.PluginLoader with manifest-based loading
- **Configuration Model**: Added CryptoPluginConfiguration with regional profiles support
- **Dependency Injection**: Extended DI to support plugin-based crypto provider registration
- **Regional Configs**: Created appsettings.crypto.{international,russia,eu,china}.yaml
- **CI Workflow**: Added .gitea/workflows/crypto-compliance.yml for audit enforcement

### Phase 2: Code Refactoring
- **API Extension**: Added ICryptoProvider.CreateEphemeralVerifier for verification-only scenarios
- **Plugin Implementation**: Created OfflineVerificationCryptoProvider with ephemeral verifier support
  - Supports ES256/384/512, RS256/384/512, PS256/384/512
  - SubjectPublicKeyInfo (SPKI) public key format
- **100% Compliance**: Refactored DsseVerifier to remove all BouncyCastle cryptographic usage
- **Unit Tests**: Created OfflineVerificationProviderTests with 39 passing tests
- **Documentation**: Created comprehensive security guide at docs/security/offline-verification-crypto-provider.md
- **Audit Infrastructure**: Created scripts/audit-crypto-usage.ps1 for static analysis

### Testing Infrastructure (TestKit)
- **Determinism Gate**: Created DeterminismGate for reproducibility validation
- **Test Fixtures**: Added PostgresFixture and ValkeyFixture using Testcontainers
- **Traits System**: Implemented test lane attributes for parallel CI execution
- **JSON Assertions**: Added CanonicalJsonAssert for deterministic JSON comparisons
- **Test Lanes**: Created test-lanes.yml workflow for parallel test execution

### Documentation
- **Architecture**: Created CRYPTO_CONFIGURATION_DRIVEN_ARCHITECTURE.md master plan
- **Sprint Tracking**: Created SPRINT_1000_0007_0002_crypto_refactoring.md (COMPLETE)
- **API Documentation**: Updated docs2/cli/crypto-plugins.md and crypto.md
- **Testing Strategy**: Created testing strategy documents in docs/implplan/SPRINT_5100_0007_*

## Compliance & Testing

- ✅ Zero direct System.Security.Cryptography usage in production code
- ✅ All crypto operations go through ICryptoProvider abstraction
- ✅ 39/39 unit tests passing for OfflineVerificationCryptoProvider
- ✅ Build successful (AirGap, Crypto plugin, DI infrastructure)
- ✅ Audit script validates crypto boundaries

## Files Modified

**Core Crypto Infrastructure:**
- src/__Libraries/StellaOps.Cryptography/CryptoProvider.cs (API extension)
- src/__Libraries/StellaOps.Cryptography/CryptoSigningKey.cs (verification-only constructor)
- src/__Libraries/StellaOps.Cryptography/EcdsaSigner.cs (fixed ephemeral verifier)

**Plugin Implementation:**
- src/__Libraries/StellaOps.Cryptography.Plugin.OfflineVerification/ (new)
- src/__Libraries/StellaOps.Cryptography.PluginLoader/ (new)

**Production Code Refactoring:**
- src/AirGap/StellaOps.AirGap.Importer/Validation/DsseVerifier.cs (100% compliant)

**Tests:**
- src/__Libraries/__Tests/StellaOps.Cryptography.Plugin.OfflineVerification.Tests/ (new, 39 tests)
- src/__Libraries/__Tests/StellaOps.Cryptography.PluginLoader.Tests/ (new)

**Configuration:**
- etc/crypto-plugins-manifest.json (plugin registry)
- etc/appsettings.crypto.*.yaml (regional profiles)

**Documentation:**
- docs/security/offline-verification-crypto-provider.md (600+ lines)
- docs/implplan/CRYPTO_CONFIGURATION_DRIVEN_ARCHITECTURE.md (master plan)
- docs/implplan/SPRINT_1000_0007_0002_crypto_refactoring.md (Phase 2 complete)

## Next Steps

Phase 3: Docker & CI/CD Integration
- Create multi-stage Dockerfiles with all plugins
- Build regional Docker Compose files
- Implement runtime configuration selection
- Add deployment validation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs2/signals/contract-mapping.md

@@ -0,0 +1,34 @@
+# Signal contract mapping
+
+StellaOps implements advisory signal contracts using domain-specific models.
+The signals align to five core concepts:
+
+Mapping summary
+| Advisory signal | StellaOps equivalent | Purpose |
+| --- | --- | --- |
+| Signal-10 (SBOM intake) | SBOM ingestion + callgraph ingest | Normalize SBOMs and call graphs with tenant and source metadata. |
+| Signal-12 (Evidence) | in-toto statements + DSSE envelopes | Signed attestations and evidence bundles. |
+| Signal-14 (Triage fact) | Triage finding, reachability, risk, and VEX entities | Aggregated facts for a vuln and component. |
+| Signal-16 (Diff delta) | Triage snapshot + smart-diff + drift causes | Deterministic change detection between runs. |
+| Signal-18 (Decision) | Triage decision + policy decision attestation | Final decision with rationale and signatures. |
+
+Evidence references
+- DSSE envelopes are addressed by sha256 of the envelope payload.
+- CAS URIs reference content-addressed evidence blobs (graphs, traces).
+
+Idempotency
+- Event envelopes include explicit idempotency keys.
+- Findings use stable identifiers derived from CVE and subject context.
+
+API surface alignment
+- SBOM ingest endpoints map to scanner and signals ingest.
+- Decision and diff endpoints map to triage and smart-diff APIs.
+
+Key equivalence guarantees
+- Subject digests and PURLs are preserved across ingestion and triage.
+- Reachability and VEX evidence is attached to findings, not rewritten.
+- Decisions carry rationale and policy references suitable for audit.
+
+Related references
+- docs/architecture/signal-contract-mapping.md
+- docs/07_HIGH_LEVEL_ARCHITECTURE.md