docs: cut CLAUDE.md to rules-only (179 → 74 lines)

CLAUDE.md now carries only what must be known *before* opening a file:
hard rules, gotchas, and an entry-point table. Everything descriptive
moved to the doc that lives next to the code.

Moved out:
- stack versions, plugin roles, asset pipeline, nav shape, user/ repo
  tracking rules → docs/reference/architecture.md
- Playwright layout, config facts, auth-setup project, test account
  → docs/reference/testing.md (new)
- folder map, full make command list (build/test/demo/worktree targets
  that only existed in CLAUDE.md) → README.md
- dev/prod Twig settings table → already in docs/guides/deploy-cycle.md

Fixed while verifying, all of them descriptions that had drifted:
- demo fixtures were listed as italy-2026-demo + no-photos-demo; the
  actual folders are italy-2025 + italy-2026-demo
- the map engine was cited at js/src/maplibre-utils.js; it is
  js/maplibre-utils.js, a hand-authored file beside the bundles
- the build-output list omitted fonts/ and the generated
  templates/partials/weather-icons.html.twig, and did not flag that
  js/maplibre-utils.js and js/nav.js are sources living in js/
- README called user/ a "standalone git repo" (it is a submodule)
- docs/README.md linked to a non-existent working/production-todo.md
- git-sync-notes.md pointed at "CLAUDE.md §1", a section number that
  no longer exists

Net: ~17.1k → ~8.5k chars of always-loaded context.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/working/git-sync-notes.md

@@ -3,7 +3,8 @@
 ## ⚠️ Config lives in the ENVIRONMENT tree, not `user/config/` (IMPORTANT)
 
 Prod has a per-environment override directory `user/env/<hostname>/config/`
-(created for Twig prod-mode — see CLAUDE.md §1). **A crucial Grav side effect:
+(created for Twig prod-mode — see [`../guides/deploy-cycle.md`](../guides/deploy-cycle.md) →
+"The env override tree"). **A crucial Grav side effect:
 once that env dir exists, the Admin panel saves ALL config changes — system and
 plugin — into the active environment's config tree**, not `user/config/`.