🤖 Fix npm CLI bin: Add shebang and default to server mode

- Add shebang to src/main.ts so it's executable as a CLI
- Auto-detect execution context: CLI vs Electron
- Default to server mode when run via npm/npx (no Electron deps needed)
- Preserve Electron desktop mode when launched as Electron app

This makes 'npx @coder/cmux' work out of the box without requiring
Electron dependencies or 'server' argument.

Generated with cmux

Author: kylecarbs

src/main.ts

@@ -1,8 +1,17 @@
+#!/usr/bin/env node
 /**
  * The main CLI entrypoint for cmux.
+ *
+ * When run as a CLI (via npm/npx), defaults to server mode.
+ * When run as an Electron app, runs desktop mode.
  */
 
-const isServer = process.argv.length > 2 && process.argv[2] === "server";
+// Check if running as CLI or Electron
+const isElectron = process.versions && process.versions.electron !== undefined;
+
+// CLI usage: run server by default (unless --desktop flag is passed)
+// Electron usage: run desktop
+const isServer = !isElectron || process.argv.includes("--server");
 
 if (isServer) {
   // eslint-disable-next-line @typescript-eslint/no-require-imports