docs: Archive Sprint 3500 (PoE), Sprint 7100 (Proof Moats), and additional sprints

Archive completed sprint documentation and deliverables:

## SPRINT_3500 - Proof of Exposure (PoE) Implementation (COMPLETE ✅)
- Windows filesystem hash sanitization (colon → underscore)
- Namespace conflict resolution (Subgraph → PoESubgraph)
- Mock test improvements with It.IsAny<>()
- Direct orchestrator unit tests
- 8/8 PoE tests passing (100% success)
- Archived to: docs/implplan/archived/2025-12-23-sprint-3500-poe/

## SPRINT_7100.0001 - Proof-Driven Moats Core (COMPLETE ✅)
- Four-tier backport detection system
- 9 production modules (4,044 LOC)
- Binary fingerprinting (TLSH + instruction hashing)
- VEX integration with proof-carrying verdicts
- 42+ unit tests passing (100% success)
- Archived to: docs/implplan/archived/2025-12-23-sprint-7100-proof-moats/

## SPRINT_7100.0002 - Proof Moats Storage Layer (COMPLETE ✅)
- PostgreSQL repository implementations
- Database migrations (4 evidence tables + audit)
- Test data seed scripts (12 evidence records, 3 CVEs)
- Integration tests with Testcontainers
- <100ms proof generation performance
- Archived to: docs/implplan/archived/2025-12-23-sprint-7100-proof-moats/

## SPRINT_3000_0200 - Authority Admin & Branding (COMPLETE ✅)
- Console admin RBAC UI components
- Branding editor with tenant isolation
- Authority backend endpoints
- Archived to: docs/implplan/archived/

## Additional Documentation
- CLI command reference and compliance guides
- Module architecture docs (26 modules documented)
- Data schemas and contracts
- Operations runbooks
- Security risk models
- Product roadmap

All archived sprints achieved 100% completion of planned deliverables.

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

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

docs2/release/release-engineering.md

@@ -0,0 +1,43 @@
+# Release engineering
+
+Release engineering turns main into signed, reproducible, airgap friendly
+artifacts. Builds must be deterministic and verifiable offline.
+
+Release philosophy
+- Every commit on main is releasable.
+- Builds are reproducible and offline friendly.
+- All artifacts ship with SBOMs and signatures.
+
+Versioning and branches
+- main: nightly images
+- release/X.Y: stabilization branch
+- tags X.Y.Z: signed releases
+
+Pipeline stages (high level)
+- Lint, unit tests, build, container tests
+- SBOM generation and provenance
+- Signing and publishing
+- End to end tests and notifications
+
+Artifact signing
+- Cosign for containers and bundles
+- DSSE envelopes for attestations
+- Optional Rekor anchoring when available
+
+Offline update kit (OUK)
+- Monthly bundle of feeds and tooling
+- Signed tarball with hashes and offline token
+
+Release checks
+- Verify SBOM attachment and signatures
+- Run release verifier scripts
+- Smoke test offline kit
+
+Hotfixes
+- Branch from latest tag, minimal patch, retag and publish
+
+Related references
+- docs/13_RELEASE_ENGINEERING_PLAYBOOK.md
+- docs/ci/*
+- docs/devops/*
+- docs/release/* and docs/releases/*