Browser MCP tools gain a global isDisabled kill-switch

What

The Chrome/browser MCP tool-call path now checks isDisabled?.() before doing any work, across dispatch, tabs_context lookup, switch_browser, list_connected_browsers, select_browser, connection watchers, and tool listing. When it's disabled:

• list_connected_browsers returns Unknown tool: list_connected_browsers instead of running.
• switch_browser and the computer-use 'type' action return a disabled/'Unknown tool' response instead of proceeding.
• select_browser returns Unknown tool: select_browser; its success message also changed from 'Connected to browser' to 'Selected browser'.

Why

This gives Claude Code a single, central way to turn off browser-control tools entirely (for example, in an environment where automated browser control shouldn't be available) rather than needing each tool to fail in its own way.