feat(web): add Serper.dev search provider & fix composer button layout overflow #208 and #207

[Gaurxvv]

• Implemented SerperProvider using Google Search API on Serper.dev in coworker/web/providers.py.
• Registered and exported the new provider in coworker/web/init.py.
• Added unit test coverage to tests/test_web_search.py verifying search provider key requirements and API response parsing.
• Redesigned the "Stop" button in the frontend Composer.tsx to be a circular red icon button to prevent layout overflow in narrow viewports.
• Added Node type declarations to package.json in surfaces/gui to fix typescript compiler issues.

[Gaurxvv]

this pr addresses issue #208: Control button UI overflow by doing the following:
When the side panel is open, the available width for the chat composer becomes smaller. The model picker was allowed to hold onto too much width, so the “Stop” button could be pushed outside the composer.
The fix does three small things:
Allows the composer’s control row to shrink.