feat: support OPENCODE_SERVER_PORT and OPENCODE_SERVER_HOSTNAME env vars (#1157)

Add support for customizing the OpenCode server port and hostname via
environment variables. This enables orchestration tools like Open Agent
to run multiple concurrent missions without port conflicts.

Environment variables:
- OPENCODE_SERVER_PORT: Custom port for the OpenCode server
- OPENCODE_SERVER_HOSTNAME: Custom hostname for the OpenCode server

When running oh-my-opencode in parallel (e.g., multiple missions in
Open Agent), each instance can now use a unique port to avoid conflicts
with the default port 4096.

src/cli/run/runner.ts

@@ -31,8 +31,18 @@ export async function run(options: RunOptions): Promise<number> {
   }
 
   try {
+    // Support custom OpenCode server port via environment variable
+    // This allows Open Agent and other orchestrators to run multiple
+    // concurrent missions without port conflicts
+    const serverPort = process.env.OPENCODE_SERVER_PORT
+      ? parseInt(process.env.OPENCODE_SERVER_PORT, 10)
+      : undefined
+    const serverHostname = process.env.OPENCODE_SERVER_HOSTNAME || undefined
+
     const { client, server } = await createOpencode({
       signal: abortController.signal,
+      ...(serverPort && !isNaN(serverPort) ? { port: serverPort } : {}),
+      ...(serverHostname ? { hostname: serverHostname } : {}),
     })
 
     const cleanup = () => {