docs: prune private-era planning notes

- Replace detailed historical planning files with concise public history docs
- Move approval packet checklist into the active writeback safety model
- Update doc-contract tests to assert against active public docs

Tests: python3 -m pytest -q -p no:cacheprovider; ruff check src/ tests/; markdown local link check; gitleaks detect --source . --redact --verbose; CI test (3.11) passed

Author: saagpatel

README.md

@@ -110,7 +110,7 @@ Treat campaign/writeback, GitHub Projects, Notion sync, catalog overrides, score
 - Workbook tour: [docs/workbook-tour.md](docs/workbook-tour.md)
 - Extending analyzers: [docs/extending-analyzers.md](docs/extending-analyzers.md)
 - Release gates: [docs/release-gates.md](docs/release-gates.md)
-- Historical implementation notes: [docs/plans/](docs/plans/) records prior roadmap and closeout context. Treat current product docs and code as authoritative.
+- Project history: [docs/project-history.md](docs/project-history.md)
 
 ## Features
 

docs/architecture.md

@@ -487,9 +487,9 @@ docs/
   architecture.md
   doctor-release-standard.md     — doctor/release-check standard for strategic repos
   modes.md
+  project-history.md
   weekly-review.md
   writeback-safety-model.md
-  plans/
 
 output/
   *.json