feat: eager vLLM warmup and smart page titles in paginate stage

- Add warmup() to LlmProvider interface for eager subprocess startup
- ManagedVllmProvider.warmup() starts vLLM in background on project load
- ProviderRegistry.warmupAll() triggers all managed providers
- NamedProvider proxies warmup() to inner provider
- paginate stage generates LLM-powered descriptive page titles when
  available, cached by content hash, falls back to generic "Page N"
- project-mcp-endpoint calls warmupAll() on router creation so vLLM
  is loading while the session initializes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/mcpd/tests/project-service.test.ts

@@ -12,6 +12,7 @@ function makeProject(overrides: Partial<ProjectWithRelations> = {}): ProjectWith
     description: '',
     ownerId: 'user-1',
     proxyMode: 'direct',
+    proxyModel: '',
     gated: true,
     llmProvider: null,
     llmModel: null,