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>

CHANGELOG.md

@@ -1,5 +1,18 @@
 # Changelog
 
+## [0.11.14.0] - 2026-03-24 — Windows Browse Fix
+
+### Fixed
+
+- **Browse engine now works on Windows.** Three compounding bugs blocked all Windows `/browse` users: the server process died when the CLI exited (Bun's `unref()` doesn't truly detach on Windows), the health check never ran because `process.kill(pid, 0)` is broken in Bun binaries on Windows, and Chromium's sandbox failed when spawned through the Bun→Node process chain. All three are now fixed. Credits to @fqueiro (PR #191) for identifying the `detached: true` approach.
+- **Health check runs first on all platforms.** `ensureServer()` now tries an HTTP health check before falling back to PID-based detection — more reliable on every OS, not just Windows.
+- **Startup errors are logged to disk.** When the server fails to start, errors are written to `~/.gstack/browse-startup-error.log` so Windows users (who lose stderr due to process detachment) can debug.
+- **Chromium sandbox disabled on Windows.** Chromium's sandbox requires elevated privileges when spawned through the Bun→Node chain — now disabled on Windows only.
+
+### For contributors
+
+- New tests for `isServerHealthy()` and startup error logging in `browse/test/config.test.ts`
+
 ## [0.11.13.0] - 2026-03-24 — Worktree Isolation + Infrastructure Elegance
 
 ### Added