feat: add twitter session safety checks

[777genius]

Summary:

• Add Twitter/X whoami and headed login helper commands
• Read expected handle from TWITTER_HANDLE or config accounts.twitter.handle
• Add TWITTER_HEADLESS, TWITTER_PROFILE_DIR, TWITTER_BROWSER_EXECUTABLE, and TWITTER_ALLOW_ANY_HANDLE overrides
• Validate the active X account before treating the profile as ready
• Use a visible maximized persistent profile for manual login flows

Tests:

• python3 -m py_compile scripts/twitter_browser.py
• git diff --check
• staged diff reviewed for local config, accounts, tokens, cookies, and product-specific data