feat(01-05): add HTTP server with health endpoint and PID file

- CoordinationServer class using node:http
- GET /health returns status, uptime, processCount
- GET /status returns full server state and process list
- PID file at ~/.cw/server.pid prevents duplicate servers
- CLI --server flag and --port option for server mode
- CW_PORT env var support for custom port

src/cli/index.ts

@@ -2,17 +2,66 @@
  * Codewalk District CLI
  *
  * Commander-based CLI with help system and version display.
+ * Supports server mode via --server flag.
  */
 
 import { Command } from 'commander';
 import { VERSION } from '../index.js';
+import { CoordinationServer } from '../server/index.js';
+import { ProcessManager, ProcessRegistry } from '../process/index.js';
+import { LogManager } from '../logging/index.js';
+
+/** Environment variable for custom port */
+const CW_PORT_ENV = 'CW_PORT';
+
+/**
+ * Starts the coordination server in foreground mode.
+ * Server runs until terminated via SIGTERM/SIGINT.
+ */
+async function startServer(port?: number): Promise<void> {
+  // Get port from option, env var, or default
+  const serverPort = port ??
+    (process.env[CW_PORT_ENV] ? parseInt(process.env[CW_PORT_ENV], 10) : undefined);
+
+  // Create dependencies
+  const registry = new ProcessRegistry();
+  const processManager = new ProcessManager(registry);
+  const logManager = new LogManager();
+
+  // Create and start server
+  const server = new CoordinationServer(
+    { port: serverPort },
+    processManager,
+    logManager
+  );
+
+  try {
+    await server.start();
+  } catch (error) {
+    console.error('Failed to start server:', (error as Error).message);
+    process.exit(1);
+  }
+
+  // Import shutdown handler (will be implemented in Task 2)
+  // For now, just handle basic signals
+  const handleSignal = async (signal: string) => {
+    console.log(`\nReceived ${signal}, shutting down...`);
+    await server.stop();
+    await processManager.stopAll();
+    process.exit(0);
+  };
+
+  process.on('SIGTERM', () => handleSignal('SIGTERM'));
+  process.on('SIGINT', () => handleSignal('SIGINT'));
+}
 
 /**
  * Creates and configures the CLI program.
  *
+ * @param serverHandler - Optional handler to be called for server mode
  * @returns Configured Commander program ready for parsing
  */
-export function createCli(): Command {
+export function createCli(serverHandler?: (port?: number) => Promise<void>): Command {
   const program = new Command();
 
   program
@@ -20,6 +69,21 @@ export function createCli(): Command {
     .description('Multi-agent workspace for orchestrating multiple Claude Code agents')
     .version(VERSION, '-v, --version', 'Display version number');
 
+  // Server mode option (global flag)
+  program
+    .option('-s, --server', 'Start the coordination server')
+    .option('-p, --port <number>', 'Port for the server (default: 3847, env: CW_PORT)', parseInt);
+
+  // Handle the case where --server is provided without a command
+  // This makes --server work as a standalone action
+  program.hook('preAction', async (_thisCommand, _actionCommand) => {
+    const opts = program.opts();
+    if (opts.server && serverHandler) {
+      await serverHandler(opts.port);
+      process.exit(0);
+    }
+  });
+
   // Placeholder commands - will be implemented in later phases
   program
     .command('status')
@@ -44,3 +108,27 @@ export function createCli(): Command {
 
   return program;
 }
+
+/**
+ * Runs the CLI, handling server mode and commands.
+ */
+export async function runCli(): Promise<void> {
+  // Check for server flag early, before Commander processes
+  const hasServerFlag = process.argv.includes('--server') || process.argv.includes('-s');
+
+  if (hasServerFlag) {
+    // Get port from args if present
+    const portIndex = process.argv.findIndex(arg => arg === '-p' || arg === '--port');
+    const port = portIndex !== -1 && process.argv[portIndex + 1]
+      ? parseInt(process.argv[portIndex + 1], 10)
+      : undefined;
+
+    await startServer(port);
+    // Server runs indefinitely until signal
+    return;
+  }
+
+  // Normal CLI processing
+  const program = createCli();
+  program.parse(process.argv);
+}