§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/ProjectLayout.test.jsx

@@ -0,0 +1,58 @@
+import React from 'react'
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { render, screen, waitFor } from '@testing-library/react'
+import { MemoryRouter, Routes, Route } from 'react-router-dom'
+import ProjectLayout from './ProjectLayout.jsx'
+
+vi.mock('../api', () => ({ getProject: vi.fn() }))
+vi.mock('../context/DeploymentProvider', () => ({
+  useDeployment: () => ({ defaultProjectId: 'default', name: 'Dep', projects: [] }),
+}))
+import { getProject } from '../api'
+
+function renderAt(path) {
+  return render(
+    <MemoryRouter initialEntries={[path]}>
+      <Routes>
+        <Route path="/p/:projectId/*" element={
+          <ProjectLayout><div data-testid="corpus">CORPUS</div></ProjectLayout>
+        } />
+      </Routes>
+    </MemoryRouter>,
+  )
+}
+
+describe('ProjectLayout', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    document.documentElement.style.removeProperty('--c-accent')
+  })
+
+  it('renders the corpus children for the corpus-served default project', async () => {
+    getProject.mockResolvedValue({ id: 'default', name: 'OHM', type: 'document', theme: {} })
+    renderAt('/p/default/')
+    expect(await screen.findByTestId('corpus')).toBeInTheDocument()
+  })
+
+  it('applies the project theme to :root and resets it on unmount', async () => {
+    getProject.mockResolvedValue({ id: 'default', name: 'OHM', type: 'document', theme: { accent: '#123456' } })
+    const { unmount } = renderAt('/p/default/')
+    await waitFor(() =>
+      expect(document.documentElement.style.getPropertyValue('--c-accent')).toBe('#123456'))
+    unmount()
+    expect(document.documentElement.style.getPropertyValue('--c-accent')).toBe('')
+  })
+
+  it('shows the not-served placeholder for a non-default (Plan-B) project', async () => {
+    getProject.mockResolvedValue({ id: 'other', name: 'Ecomm', type: 'bdd', theme: {} })
+    renderAt('/p/other/')
+    expect(await screen.findByText(/isn.t being served here yet/i)).toBeInTheDocument()
+    expect(screen.queryByTestId('corpus')).not.toBeInTheDocument()
+  })
+
+  it('shows a not-found message when the project 404s', async () => {
+    getProject.mockRejectedValue(Object.assign(new Error('nope'), { status: 404 }))
+    renderAt('/p/ghost/')
+    expect(await screen.findByText(/Not found/i)).toBeInTheDocument()
+  })
+})