feat: persistent profile mode for enterprise SSO (BROWSE_PROFILE_DIR)

[haha1903]

Summary

• Add opt-in persistent browser profile support via BROWSE_PROFILE_DIR env var
• When set, uses chromium.launchPersistentContext() instead of chromium.launch() + newContext(), which preserves SSO sessions, device certs, and browser extensions across commands
• Add BROWSE_CHANNEL env var to use system Chrome/Edge instead of bundled Chromium
• Automatically removes Playwright defaults (--disable-extensions, --use-mock-keychain, --password-store=basic) that break enterprise auth flows

This enables headless access to enterprise sites protected by macOS Platform SSO, Intune device compliance, and Azure AD Conditional Access — without any UI popups or manual login.

Default behavior is completely unchanged. Only activates when BROWSE_PROFILE_DIR is set.

Usage

export BROWSE_PROFILE_DIR=~/.gstack/browse-chrome-profile
export BROWSE_CHANNEL=chrome
$B goto https://internal-site.example.com
$B text  # works with SSO, no login needed

How it works

Playwright's bundled Chromium launches with --disable-extensions and --use-mock-keychain by default, which disables macOS Platform SSO Extension and blocks real Keychain access. Enterprise SSO (Azure AD, Okta, etc.) relies on these OS-level hooks.

launchPersistentContext() with a dedicated profile dir + ignoreDefaultArgs for the SSO-breaking flags is the same approach used by Google's Chrome DevTools MCP (via Puppeteer). This PR brings the same capability to Playwright.

Changes

File	Change
browse/src/browser-manager.ts	buildLaunchConfig() helper, persistent profile launch path, guards for close(), isHealthy(), recreateContext(), handoff()
browse/src/meta-commands.ts	status shows persistent mode info

Test plan

• Default mode: $B goto https://example.com works as before (no env vars set)
• Enterprise mode: set BROWSE_PROFILE_DIR + BROWSE_CHANNEL=chrome, verify SSO-protected sites load
• $B status shows Mode: persistent-profile when active
• $B handoff works in persistent mode (close + relaunch headed)
• useragent command returns graceful message in persistent mode

🤖 Generated with Claude Code