fix(browse): suppress remaining Windows console-window flashes

On Windows the browse tool pops console windows during normal use. #1979 fixes
one source (the watchdog's tasklist → conhost flash every 60s). This addresses
the other three:

- chrome-headless-shell.exe (every browse action): the default headless path
  launches the console-subsystem headless shell, which pops a window. Force
  Chrome's "new" headless (full chrome.exe, GUI-subsystem → no console window)
  on Windows via --headless=new. Other platforms keep the lighter shell.
- node daemon (detached spawn on Windows): detached spawns create a console
  window unless windowsHide is set. Added it to the launcher + the detached
  server spawn.
- bun terminal-agent: spawned via Bun.spawn, whose windowsHide does not
  reliably suppress the window on Windows. Switched to Node's child_process
  .spawn with windowsHide (reliable), same unref'd lifecycle.

Verified on Win11: no chrome-headless-shell process (chrome.exe --headless=new
in the cmdline), screenshots render correctly, single daemon, no stray bun
windows.

browse/src/browser-manager.ts

@@ -369,6 +369,16 @@ export class BrowserManager {
       console.log(`[browse] Extensions loaded from: ${extensionsDir}`);
     }
 
+    // Windows: the default headless path launches chrome-headless-shell.exe — a
+    // CONSOLE-subsystem binary that pops a terminal window on every launch. Switch
+    // to Chrome's "new" headless (full chrome.exe, GUI-subsystem → no console
+    // window) by launching non-headless with --headless=new. Other platforms keep
+    // the lighter headless shell (they have no console-window problem).
+    if (process.platform === 'win32' && useHeadless) {
+      launchArgs.push('--headless=new');
+      useHeadless = false;
+    }
+
     this.browser = await chromium.launch({
       headless: useHeadless,
       // On Windows, Chromium's sandbox fails when the server is spawned through

browse/src/cli.ts

@@ -323,9 +323,11 @@ async function startServer(extraEnv?: Record<string, string>): Promise<ServerSta
     const launcherCode =
       `const{spawn}=require('child_process');` +
       `spawn(process.execPath,[${JSON.stringify(NODE_SERVER_SCRIPT)}],` +
-      `{detached:true,stdio:['ignore','ignore','ignore'],env:Object.assign({},process.env,` +
+      // windowsHide: a detached spawn on Windows pops a console window unless
+      // explicitly hidden — this flashed on every daemon (re)start.
+      `{detached:true,windowsHide:true,stdio:['ignore','ignore','ignore'],env:Object.assign({},process.env,` +
       `${extraEnvStr})}).unref()`;
-    Bun.spawnSync(['node', '-e', launcherCode], { stdio: ['ignore', 'ignore', 'ignore'] });
+    Bun.spawnSync(['node', '-e', launcherCode], { stdio: ['ignore', 'ignore', 'ignore'], windowsHide: true });
   } else {
     // macOS/Linux: Bun.spawn().unref() only removes the child from Bun's event
     // loop — it does NOT call setsid(), so the spawned server stays in the

browse/src/terminal-agent-control.ts

@@ -16,6 +16,7 @@
  */
 import * as fs from 'fs';
 import * as path from 'path';
+import { spawn as nodeSpawn } from 'child_process';
 import { safeUnlink, safeKill, isProcessAlive } from './error-handling';
 import { writeSecureFile, mkdirSecure } from './file-permissions';
 
@@ -68,7 +69,10 @@ export function spawnTerminalAgent(opts: {
   }
   const script = opts.scriptPath || resolveTerminalAgentScript();
   if (!script || !fs.existsSync(script)) return null;
-  const proc = (Bun as any).spawn(['bun', 'run', script], {
+  // Spawn via Node's child_process (not Bun.spawn): Node's `windowsHide` reliably
+  // suppresses the console window on Windows, whereas Bun's does not. Same lifecycle:
+  // an unref'd child so it doesn't hold the parent's event loop open.
+  const proc = nodeSpawn('bun', ['run', script], {
     cwd: opts.cwd || process.cwd(),
     env: {
       ...process.env,
@@ -77,6 +81,7 @@ export function spawnTerminalAgent(opts: {
       ...(opts.extraEnv || {}),
     },
     stdio: ['ignore', 'ignore', 'ignore'],
+    windowsHide: true,
   });
   proc.unref?.();
   return proc.pid ?? null;