Migrates tools/browser_providers/browserbase.py → plugins/browser/browserbase/.
Direct credentials only (BROWSERBASE_API_KEY + BROWSERBASE_PROJECT_ID); same
session-creation, 402-handling, and feature-flag logic as the legacy
implementation. Renames is_configured() → is_available() to match the new
BrowserProvider ABC.
The legacy module tools/browser_providers/browserbase.py is NOT yet deleted
and tools/browser_tool.py still references the in-tree class. The dispatcher
cutover happens in a later commit so the plugin migration and the dispatcher
switch land as separate reviewable units.
Verified via plugin-discovery E2E:
- browserbase registers as 'browserbase'
- is_available() correctly tracks BROWSERBASE_API_KEY + BROWSERBASE_PROJECT_ID
- _resolve('browserbase') returns the provider even when unavailable
(so dispatcher surfaces a typed credentials error)
- _resolve(None) returns the provider when it's the single eligible one
kshitijk4poor