feat: Switch to persistent Chroma HTTP server

Replace MCP subprocess approach with persistent Chroma HTTP server for
improved performance and reliability. This re-enables Chroma on Windows
by eliminating the subprocess spawning that caused console popups.

Changes:
- NEW: ChromaServerManager.ts - Manages local Chroma server lifecycle
  via `npx chroma run`
- REFACTOR: ChromaSync.ts - Uses chromadb npm package's ChromaClient
  instead of MCP subprocess (removes Windows disabling)
- UPDATE: worker-service.ts - Starts Chroma server on initialization
- UPDATE: GracefulShutdown.ts - Stops Chroma server on shutdown
- UPDATE: SettingsDefaultsManager.ts - New Chroma configuration options
- UPDATE: build-hooks.js - Mark optional chromadb deps as external

Benefits:
- Eliminates subprocess spawn latency on first query
- Single server process instead of per-operation subprocesses
- No Python/uvx dependency for local mode
- Re-enables Chroma vector search on Windows
- Future-ready for cloud-hosted Chroma (claude-mem pro)
- Cross-platform: Linux, macOS, Windows

Configuration:
  CLAUDE_MEM_CHROMA_MODE=local|remote
  CLAUDE_MEM_CHROMA_HOST=127.0.0.1
  CLAUDE_MEM_CHROMA_PORT=8000
  CLAUDE_MEM_CHROMA_SSL=false

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/infrastructure/GracefulShutdown.ts

@@ -29,6 +29,13 @@ export interface CloseableDatabase {
   close(): Promise<void>;
 }
 
+/**
+ * Stoppable service interface for Chroma server
+ */
+export interface StoppableServer {
+  stop(): Promise<void>;
+}
+
 /**
  * Configuration for graceful shutdown
  */
@@ -37,6 +44,7 @@ export interface GracefulShutdownConfig {
   sessionManager: ShutdownableService;
   mcpClient?: CloseableClient;
   dbManager?: CloseableDatabase;
+  chromaServer?: StoppableServer;
 }
 
 /**
@@ -76,7 +84,14 @@ export async function performGracefulShutdown(config: GracefulShutdownConfig): P
     await config.dbManager.close();
   }
 
-  // STEP 6: Force kill any remaining child processes (Windows zombie port fix)
+  // STEP 6: Stop Chroma server (local mode only)
+  if (config.chromaServer) {
+    logger.info('SHUTDOWN', 'Stopping Chroma server...');
+    await config.chromaServer.stop();
+    logger.info('SHUTDOWN', 'Chroma server stopped');
+  }
+
+  // STEP 7: Force kill any remaining child processes (Windows zombie port fix)
   if (childPids.length > 0) {
     logger.info('SYSTEM', 'Force killing remaining children');
     for (const pid of childPids) {