feat(browse): add Edge/Chrome channel support via BROWSE_BROWSER=edge

[HMAKT99]

Summary

• BROWSE_BROWSER=edge launches user's installed Edge via Playwright channel system
• BROWSE_BROWSER=chrome launches user's installed Chrome (not bundled Chromium)
• Uses channel: 'msedge' / channel: 'chrome' — same Chromium engine, user's binary
• When unset: zero behavior change (bundled Chromium)

BROWSE_BROWSER=edge browse server       # user's Edge
BROWSE_BROWSER=chrome browse server     # user's Chrome
browse server                           # bundled Chromium (unchanged)

Depends on: #371 (Firefox PR introduces the refactor this builds on).

1 file, 19 lines changed

browse/src/browser-manager.ts

Test plan

• All 548 existing tests pass
• Default: bundled chromium unchanged
• edge → channel: 'msedge', chrome → channel: 'chrome'

[garrytan]

Thanks for this! Closing — Edge/Chrome channel support isn't something we've had user demand for. We're keeping the browser scope focused on standard Chromium for now. Appreciate the effort!