§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/src/components/Inbox.jsx

@@ -17,6 +17,7 @@ import {
   markNotificationRead,
   markNotificationsReadByFilter,
 } from '../api.js'
+import { entryPath, entryPrPath, useProjectId } from '../lib/entryPaths'
 import './Inbox.css'
 
 const CATEGORIES = [
@@ -228,11 +229,12 @@ function ContributionRequestRow({ item, onMarkRead }) {
 }
 
 function InboxRow({ item, onClick, onMarkRead, onClose }) {
+  const pid = useProjectId()
   if (item.event_kind === 'contribution_request_on_pending_rfc') {
     return <ContributionRequestRow item={item} onMarkRead={onMarkRead} />
   }
   const unread = !item.read_at
-  const target = deepLink(item)
+  const target = deepLink(item, pid)
   const handle = async () => {
     await onClick(item)
     if (target) onClose?.()
@@ -277,10 +279,10 @@ function InboxRow({ item, onClick, onMarkRead, onClose }) {
   )
 }
 
-function deepLink(item) {
-  if (item.rfc_slug && item.pr_number) return `/rfc/${item.rfc_slug}/pr/${item.pr_number}`
-  if (item.rfc_slug && item.branch_name) return `/rfc/${item.rfc_slug}?branch=${item.branch_name}`
-  if (item.rfc_slug) return `/rfc/${item.rfc_slug}`
+function deepLink(item, pid) {
+  if (item.rfc_slug && item.pr_number) return entryPrPath(pid, item.rfc_slug, item.pr_number)
+  if (item.rfc_slug && item.branch_name) return `${entryPath(pid, item.rfc_slug)}?branch=${item.branch_name}`
+  if (item.rfc_slug) return entryPath(pid, item.rfc_slug)
   return ''
 }