feat: pair-agent auto-launches headed mode before pairing

When pair-agent detects headless mode, it auto-switches to headed
(visible Chromium window) so the user can watch what the remote
agent does. Use --headless to skip this. Fixed compiled binary
path resolution (process.execPath, not process.argv[1] which is
virtual /$bunfs/ in Bun compiled binaries).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

browse/src/cli.ts

@@ -922,10 +922,31 @@ Refs:           After 'snapshot', use @e1, @e2... as selectors:
     commandArgs.push(stdin.trim());
   }
 
-  const state = await ensureServer();
+  let state = await ensureServer();
 
   // ─── Pair-Agent (post-server, pre-dispatch) ──────────────
   if (command === 'pair-agent') {
+    // Ensure headed mode — the user should see the browser window
+    // when sharing it with another agent. Feels safer, more impressive.
+    if (state.mode !== 'headed' && !hasFlag(commandArgs, '--headless')) {
+      console.log('[browse] Opening GStack Browser so you can see what the remote agent does...');
+      // In compiled binaries, process.argv[1] is /$bunfs/... (virtual).
+      // Use process.execPath which is the real binary on disk.
+      const browseBin = process.execPath;
+      const connectProc = Bun.spawn([browseBin, 'connect'], {
+        cwd: process.cwd(),
+        stdio: ['ignore', 'inherit', 'inherit'],
+        env: process.env,
+      });
+      await connectProc.exited;
+      // Re-read state after headed mode switch
+      const newState = readState();
+      if (newState && await isServerHealthy(newState.port)) {
+        state = newState as ServerState;
+      } else {
+        console.warn('[browse] Could not switch to headed mode. Continuing headless.');
+      }
+    }
     await handlePairAgent(state, commandArgs);
     process.exit(0);
   }