§22 M3 frontend: /p/<project>/ routing, runtime branding, directory, 308s (v0.35.0)

Implements the M3-frontend slice of the §22 multi-project track, per
docs/superpowers/specs/2026-06-03-m3-frontend-design.md (design merged in
#10). Completes the runtime-config cut 0.33.0 (M3-backend Plan A) began.

Frontend:
- DeploymentProvider boots GET /api/deployment → {name, tagline,
  defaultProjectId, projects}; brandTitle() neutral 'RFC' pre-fetch fallback.
- /p/:projectId/* routing with generic /e/<slug> segment. ProjectLayout
  fetches /api/projects/:id, applies per-project theme (reset on switch),
  provides ProjectContext, guards the corpus (served only for the default;
  others get NotServedPlaceholder — decouples this slice from Plan B).
- Directory at / (2+ projects) with N=1 redirect into the single project;
  ProjectSwitcher in deployment chrome; entry-noun by project type.
- VITE_APP_NAME hard cut: removed from vite.config + index.html; the 6 brand
  reads now use deployment.name via context; static <title>RFC</title> + JS
  document.title. Internal /rfc·/proposals links → /p/<project>/e|proposals
  via lib/entryPaths.

Backend:
- GET /api/deployment returns default_project_id (the guard contract).
- Server-side 308s: /rfc/<slug>, /rfc/<slug>/pr/<n>, /proposals/<n> →
  /p/<default>/… . nginx (testing + prod) routes /rfc/ and /proposals/ to
  the backend.

Tests: 3 new backend redirect/deployment tests (438 pass); Vitest unit for
DeploymentProvider, ProjectLayout (theme/guard/404), Directory (11 pass);
clean build with no VITE_APP_NAME. Playwright e2e deferred until Tier-1 seeds
a registry (see CHANGELOG 0.35.0 step 5).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/.env.example

@@ -4,15 +4,10 @@
 # and dev (`npm run dev`) time. Real `.env` files are gitignored; only this
 # `.env.example` is committed.
 
-# The user-visible name of this deployment. Used as the browser tab title,
-# the header brand, and the landing page H1. Required — the framework
-# ships no default on purpose so each deployment names itself. If unset,
-# `npm run build` fails with a clear message.
-#
-# Examples:
-#   VITE_APP_NAME=Wiggleverse RFC
-#   VITE_APP_NAME=Wiggleverse Open Human Model
-VITE_APP_NAME=
+# §22.9 (M3, v0.35.0): the deployment name is NO LONGER a build-time var.
+# It comes from the registry (`projects.yaml` `deployment.name`) and is served
+# at runtime by GET /api/deployment. VITE_APP_NAME has been removed — set the
+# name in your registry repo instead, and the same build serves any deployment.
 
 # Optional contact line shown on the /beta-pending page when a deployment
 # is in private-beta mode (i.e. the backend's `allowed_emails` table has