opencode: add the OpenCode sidecar (step 1 — serve lifecycle + port report)

New officer-opencode sidecar (same philosophy as officer-claude): a singleton that owns
an `opencode serve` running from DATA_PATH/opencode-sidecar (created if missing) on a
random port, registers with the API as capability 'opencode', and reports its port via a
new `opencode:server` protocol event. The API stores it (sidecar-server.ts, wired in
server.tsx via getOpenCodeServerUrl). ecosystem.config.cjs runs the sidecar instead of a
bare pm2 serve. Turn-running + API rewiring come in later steps.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/opencode/index.ts

@@ -0,0 +1,113 @@
+import { mkdirSync } from 'node:fs';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
+import { DATA_PATH } from '../../data-path';
+import { createSidecarConnector } from '../connect';
+import type { SidecarCommand, SidecarEvent } from '../protocol';
+
+// The OpenCode sidecar (officer-opencode). Same philosophy as officer-claude: a singleton process that
+// OWNS its runtime — here, an `opencode serve` — registers with the API server, and answers commands.
+// The serve's working directory is DATA_PATH/opencode-sidecar (cwd matters: OpenCode's tools follow the
+// server cwd). It listens on a random port, reported to the API on connect so it can route there.
+
+const API_URL = process.env.API_URL ?? `ws://127.0.0.1:${process.env.PORT ?? '5000'}`;
+const OPENCODE_BIN = process.env.OPENCODE_BIN || join(homedir(), '.opencode', 'bin', 'opencode');
+const SERVE_CWD = join(DATA_PATH, 'opencode-sidecar');
+const HEALTH_TIMEOUT_MS = 20_000;
+
+/** Grab an ephemeral free port by briefly binding one and releasing it. */
+function getFreePort(): number {
+  const probe = Bun.serve({ port: 0, hostname: '127.0.0.1', fetch: () => new Response('') });
+  const port = probe.port;
+  probe.stop(true);
+  if (port == null) throw new Error('failed to acquire a free port');
+  return port;
+}
+
+async function waitHealthy(baseUrl: string, timeoutMs: number): Promise<boolean> {
+  const deadline = Date.now() + timeoutMs;
+  while (Date.now() < deadline) {
+    try {
+      const res = await fetch(`${baseUrl}/api/health`, { signal: AbortSignal.timeout(2000) });
+      if (res.ok) return true;
+    } catch {
+      /* not up yet */
+    }
+    await new Promise((r) => setTimeout(r, 200));
+  }
+  return false;
+}
+
+// ── Start the OpenCode server (cwd = DATA_PATH/opencode-sidecar) ──
+
+mkdirSync(SERVE_CWD, { recursive: true });
+const port = getFreePort();
+const baseUrl = `http://127.0.0.1:${port}`;
+
+console.log(`[opencode] starting serve on ${baseUrl} (cwd=${SERVE_CWD})`);
+const serve = Bun.spawn([OPENCODE_BIN, 'serve', '--port', String(port), '--hostname', '127.0.0.1'], {
+  cwd: SERVE_CWD,
+  stdout: 'inherit',
+  stderr: 'inherit',
+});
+
+if (!(await waitHealthy(baseUrl, HEALTH_TIMEOUT_MS))) {
+  console.error('[opencode] serve failed its health check');
+  try {
+    serve.kill();
+  } catch {
+    /* already gone */
+  }
+  process.exit(1);
+}
+console.log(`[opencode] serve healthy on port ${port}`);
+
+// ── Command handlers ──
+
+type ReplyFn = (msg: SidecarEvent) => void;
+
+function handleCommand(cmd: SidecarCommand, reply: ReplyFn) {
+  switch (cmd.type) {
+    case 'ping':
+      reply({ type: 'pong', id: cmd.id });
+      break;
+    default:
+      reply({
+        type: 'error',
+        id: (cmd as SidecarCommand).id,
+        error: `Unknown command type: ${(cmd as Record<string, unknown>).type}`,
+      });
+  }
+}
+
+// ── Register with the API server ──
+
+const connection = createSidecarConnector({
+  apiUrl: `${API_URL}/api/sidecar/register`,
+  name: 'opencode',
+  capabilities: ['opencode'],
+  onCommand(cmd, reply) {
+    handleCommand(cmd as SidecarCommand, reply as ReplyFn);
+  },
+  onConnected() {
+    // Tell the API where our OpenCode HTTP server is listening, so it can route requests there.
+    connection.send({ type: 'opencode:server', port });
+    console.log(`[opencode] reported server port ${port} to API`);
+  },
+});
+
+// ── Graceful shutdown ──
+
+function shutdown(signal: string) {
+  console.log(`[opencode] ${signal} received, stopping serve...`);
+  connection.destroy();
+  try {
+    serve.kill();
+  } catch {
+    /* already gone */
+  }
+  process.exit(0);
+}
+
+process.on('SIGTERM', () => shutdown('SIGTERM'));
+process.on('SIGINT', () => shutdown('SIGINT'));