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/db/tests/helpers.ts

@@ -28,6 +28,7 @@ export async function cleanupTestDb(): Promise<void> {
 
 export async function clearAllTables(client: PrismaClient): Promise<void> {
   // Delete in order respecting foreign keys
+  await client.auditEvent.deleteMany();
   await client.auditLog.deleteMany();
   await client.mcpInstance.deleteMany();
   await client.promptRequest.deleteMany();