docs: sync project guides to the new CI flow

Aligns the project guides with the branching/CI/environment changes
landed in the previous commits:

- CLAUDE.md: per-stage CI gate now closes against gitea.lan; describes
  the main/development/feature/* flow and the workflow surface
- docs/ARCHITECTURE.md: new section 18 "CI and Environments" covering
  branches, workflows, and the local-dev / dev-deploy / local-ci
  triad; section numbering shifted accordingly
- tools/local-ci/README.md: marked as fallback (offline / runner
  isolation only)
- tools/local-dev/README.md and ui/README.md: cross-link to
  tools/dev-deploy/ for production-shaped testing

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tools/local-ci/README.md

@@ -1,9 +1,17 @@
-# Local Gitea CI
+# Local Gitea CI (fallback)
+
+> **Status:** fallback / opt-in. The primary CI target is now
+> `gitea.lan` with its host-mode `act_runner`. The per-stage CI gate
+> closes against `gitea.lan`, not against this stack. Use this
+> directory when you want to validate `.gitea/workflows/*` without
+> reaching `gitea.lan` — for example, when iterating on a workflow
+> file from a flight without LAN access — or when isolating a runner
+> issue from production-shaped infrastructure.
 
 Self-contained Gitea + Actions runner for verifying
-`.gitea/workflows/*` honestly before pushing to a real Gitea instance.
-Runs natively on arm64 (Apple Silicon) — every image below has an
-arm64 variant, so Docker pulls the right architecture and the runner
+`.gitea/workflows/*` honestly before pushing to `gitea.lan`. Runs
+natively on arm64 (Apple Silicon) — every image below has an arm64
+variant, so Docker pulls the right architecture and the runner
 executes workflow steps without QEMU emulation.
 
 ## Prerequisites