Replace blocking alert() calls in MCP delete handlers with non-blocking deleteError state updates and setSaveStatus('error') on failure.
Thread deleteError through Settings -> Agents settings views and render inline error feedback in Claude/Codex MCP sections near delete actions.
Prevent orphaned save-close timers by clearing and nulling closeTimerRef before scheduling a new timeout, and by nulling the ref during unmount cleanup.
- Replaced old settings components with new tab-based structure for API, Git, and Tasks settings.
- Introduced hooks for managing credentials and Git settings.
- Created new sections for API keys and GitHub credentials with appropriate UI components.
