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/services/prompt-service.test.ts

@@ -43,6 +43,7 @@ function makeProject(overrides: Partial<Project> = {}): Project {
     description: '',
     prompt: '',
     proxyMode: 'direct',
+    proxyModel: '',
     gated: true,
     llmProvider: null,
     llmModel: null,
@@ -400,8 +401,8 @@ describe('PromptService', () => {
       const result = await service.getVisiblePrompts('proj-1', 'sess-1');
 
       expect(result).toHaveLength(2);
-      expect(result[0]).toEqual({ name: 'approved-1', content: 'A', type: 'prompt' });
-      expect(result[1]).toEqual({ name: 'pending-1', content: 'B', type: 'promptrequest' });
+      expect(result[0]).toMatchObject({ name: 'approved-1', content: 'A', type: 'prompt' });
+      expect(result[1]).toMatchObject({ name: 'pending-1', content: 'B', type: 'promptrequest' });
     });
 
     it('should not include pending requests without sessionId', async () => {