semi implemented and features implemented save checkpoint

docs/features/unchecked/attestor/evidence-first-security-with-dsse-envelopes.md

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+# Evidence-First Security with DSSE Envelopes
+
+## Module
+Attestor
+
+## Status
+IMPLEMENTED
+
+## Description
+All security findings are wrapped in DSSE envelopes; SmartDiff results are attested as delta verdicts and published to OCI registries.
+
+## Implementation Details
+- **DSSE Envelope Signing**: Multiple signing layers across Attestor:
+  - `src/Attestor/StellaOps.Attestor.Envelope/EnvelopeSignatureService.cs` -- core envelope signing
+  - `__Libraries/StellaOps.Attestor.ProofChain/Signing/ProofChainSigner.cs` -- proof chain signing
+  - `StellaOps.Attestor.Core/Signing/DsseSigningService.cs` -- core attestation signing
+- **Delta Verdict Attestation**: `Predicates/DeltaVerdictPredicate.cs` -- delta verdict wrapped in DSSE. `Statements/DeltaVerdictStatement.cs` -- in-toto statement.
+- **OCI Publication**: `src/Attestor/__Libraries/StellaOps.Attestor.Oci/Services/` -- `IOciAttestationAttacher.cs`, `OrasAttestationAttacher.cs` -- attaches DSSE-signed attestations to OCI images. `ISbomOciPublisher.cs`, `SbomOciPublisher.cs` -- publishes SBOMs to OCI.
+- **Trust Verdict OCI**: `__Libraries/StellaOps.Attestor.TrustVerdict/Oci/TrustVerdictOciAttacher.cs` (with `.Attach`, `.FetchList`) -- attaches trust verdicts to OCI artifacts.
+- **Evidence Predicate**: `Predicates/EvidencePredicate.cs` -- wraps security evidence in attestable predicate.
+- **Smart Diff**: `__Tests/StellaOps.Attestor.Types.Tests/SmartDiffSchemaValidationTests.cs` -- validates smart diff schema.
+- **Tests**: `__Tests/StellaOps.Attestor.Oci.Tests/OrasAttestationAttacherTests.cs`, `SbomOciPublisherTests.cs`
+
+## E2E Test Plan
+- [ ] Wrap a security finding in a DSSE envelope via `ProofChainSigner` and verify the evidence predicate is signed
+- [ ] Create a delta verdict from SmartDiff results and sign it as a DSSE envelope
+- [ ] Publish the signed delta verdict to an OCI registry via `OrasAttestationAttacher` and verify it is attached as a referrer
+- [ ] Publish an SBOM to OCI via `SbomOciPublisher` and verify the DSSE signature is attached
+- [ ] Attach a trust verdict to an OCI image via `TrustVerdictOciAttacher` and verify the referrer list includes it
+- [ ] Fetch the list of attestations for an OCI image via `TrustVerdictOciAttacher.FetchList` and verify all attached attestations are returned
+- [ ] Verify a retrieved DSSE envelope from OCI validates correctly