fix: Windows browse — health-check-first ensureServer, detached startServer, Windows process mgmt (v0.11.11.0) (#431)

* fix: Windows browse — health-check-first ensureServer, detached startServer, Windows process mgmt

Three compounding bugs made browse completely broken on Windows:

1. Bun.spawn().unref() doesn't truly detach on Windows — server dies when
   CLI exits. Fix: use Node's child_process.spawn with { detached: true }
   via a launcher script. Credit: PR #191 by @fqueiro for the approach.

2. process.kill(pid, 0) is broken in Bun's compiled binary on Windows —
   ensureServer() never reaches the health check. Fix: restructure to
   health-check-first (HTTP is definitive proof on all platforms). Extract
   isServerHealthy() helper for DRY (4 call sites).

3. Windows process management: isProcessAlive() falls back to tasklist,
   killServer() uses taskkill /T /F (kills process tree including Chromium),
   cleanupLegacyState() skips on Windows (no /tmp, no ps).

Also: hard-fail on Windows if server-node.mjs is missing instead of
silently falling back to the known-broken Bun path.

Fixes #342.

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

* fix: disable Chromium sandbox on Windows

Chromium's sandbox fails when the server is spawned through the
Bun→Node process chain on Windows (GitHub #276). Disable
chromiumSandbox on Windows at both launch sites (headless + headed).

Safe: local daemon browsing user-specified URLs, Playwright docs
recommend disabling in CI/container environments.

Fixes #276.

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

* fix: startup error log + Windows exit handler for browse server

On Windows, the CLI can't capture stderr from the server (stdio: 'ignore'
required for process detachment). Write startup errors to
.gstack/browse-startup-error.log so the CLI can report them on timeout.

Also add process.on('exit') handler on Windows as defense-in-depth for
state file cleanup (primary mechanism is CLI's stale-state detection).

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

* test: add isServerHealthy + startup error log tests

Tests for the new cross-platform health check helper (isServerHealthy)
that replaces PID-based liveness checks in all polling loops. Covers
healthy, unhealthy, unreachable, and error response cases.

Also tests the startup error log write/read format used on Windows.

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

* chore: bump version and changelog (v0.11.11.0)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: sync ARCHITECTURE.md with health-check-first ensureServer

---------

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

browse/src/browser-manager.ts

@@ -89,6 +89,10 @@ export class BrowserManager {
 
     this.browser = await chromium.launch({
       headless: useHeadless,
+      // On Windows, Chromium's sandbox fails when the server is spawned through
+      // the Bun→Node process chain (GitHub #276). Disable it — local daemon
+      // browsing user-specified URLs has marginal sandbox benefit.
+      chromiumSandbox: process.platform !== 'win32',
       ...(launchArgs.length > 0 ? { args: launchArgs } : {}),
     });
 
@@ -492,7 +496,11 @@ export class BrowserManager {
     // 2. Launch new headed browser (try-catch — if this fails, headless stays running)
     let newBrowser: Browser;
     try {
-      newBrowser = await chromium.launch({ headless: false, timeout: 15000 });
+      newBrowser = await chromium.launch({
+        headless: false,
+        timeout: 15000,
+        chromiumSandbox: process.platform !== 'win32',
+      });
     } catch (err: unknown) {
       const msg = err instanceof Error ? err.message : String(err);
       return `ERROR: Cannot open headed browser — ${msg}. Headless browser still running.`;