feat(site): retire legacy pages and refine timeline

[l0cka]

Summary

• retire Map, Agencies, Framework and Blog from public navigation, the sitemap and direct route access
• limit Policy Timeline to verified register-linked lifecycle events
• surface verified legacy announcements and milestones in Developments without duplicating canonical evidence

Why

The retired pages no longer fit the focused public product. The Timeline also mixed policy lifecycle events with announcements and milestones, blurring the boundary between the curated register and the developments feed.

Implementation

• retired routes render the Next.js not-found boundary and are removed from navigation and discovery surfaces
• added an explicit policy-register timeline scope covering introduced, amended, repealed and superseded events
• project verified non-register editorial timeline entries into Developments at read time
• deduplicate projected entries against live development records while allowing approved editorial records to supersede dismissed machine detections
• updated the API and static JSON projections, documentation and regression coverage

Impact

• /timeline now represents policy register history only
• verified announcements and milestones remain discoverable through /developments
• legacy evidence remains canonical in data/timeline.json; this change does not rewrite or delete editorial records

Validation

• npm run check
  • 39 test files and 472 tests passed
  • data validation completed with 0 errors and 3 existing editorial-review warnings
  • production build passed
• focused regression run: 3 test files and 50 tests passed
• TruffleHog exact-commit scan: 0 verified or unknown secrets
• live browser verification: Timeline shows 53 lifecycle events; Developments shows 44 verified items, including 11 projected legacy records
• exact-commit Autoreview was attempted, but external model egress was denied; the commit was reviewed locally instead