fix(browse): bump Playwright to ^1.60.0 and pin full Chromium for extension loading

[stevenbarragan]

Summary

Two related fixes for the headless browse daemon:

• Playwright bump ^1.58.2 → ^1.60.0: Chromium 1208 (bundled by 1.58.2, Chrome 145) fails Flutter Web's FlutterLoader environment compatibility check in headless mode, producing blank pages with webgl: false, no flt-glass-pane, and a pageerror: FlutterLoader could not find a build compatible with configuration and environment. Chromium 1223 (bundled by 1.60.0, Chrome 148) renders Flutter 3.41+ apps correctly in headless. Verified empirically against a Flutter 3.41.9 web build: same browser-manager.ts, same launch args, only the Chromium build differs.

• launchHeaded() explicit executablePath pin: Playwright 1.49 changed chromium.launch({ headless: true }) to use chrome-headless-shell by default. chrome-headless-shell cannot load Chrome extensions — /open-gstack-browser and /pair-agent depend on the gstack sidebar extension. The headed path (launchPersistentContext({ headless: false })) was unaffected, but we relied on that implicitly. This patch pins executablePath: GSTACK_CHROMIUM_PATH || chromium.executablePath() explicitly so future Playwright changes to launchPersistentContext defaults can't silently break extension loading.

Boundaries respected:

• GSTACK_CHROMIUM_PATH override still takes priority in both paths
• No changes to CDP allowlist, stealth args, or any non-Playwright code
• chrome-headless-shell remains the default for headless $B launches (Playwright 1.49+ behavior, unchanged)

Test plan

• bun test browse/test/browser-manager-unit.test.ts browse/test/browser-manager-custom-chromium.test.ts — 10/10 pass
• Full free test suite (bun test browse/test/ test/ make-pdf/test/ --ignore ...) — exit code 0
• $B goto https://example.com round-trips correctly
• Flutter 3.41.9 web app: blank page with webgl: false on 1.58.2 → full render with webgl: true, glass: 1, semantics: 10 on 1.60.0

🤖 Generated with Claude Code

[jzeng151]

Heads up — this bump also fixes a more severe issue not mentioned in the PR description: playwright install chromium hangs
indefinitely during extraction on Node 26+ with Playwright ≤ 1.59.x, which fully blocks ./setup for new users on those Node
versions. I hit it twice in a row today (Node v26.1.0, gstack@HEAD): zip downloads fine (167MB), then extraction stalls at
~18MB with all worker threads parked in futex_wait/do_epoll_wait and zero CPU growth.

Root cause is fd-slicer's stream _destroy lifecycle, which never emits close on Node 26 — see
microsoft/playwright#40724. The fix vendors patched yauzl 3.2.1
(microsoft/playwright#40747, merged 2026-05-09) and first ships in
Playwright v1.60.0 — exactly what this PR pulls in. Confirmed locally that bumping to ^1.60.0 lets bunx playwright install chromium complete normally.