v0.26.8: Background processes, MCP search, and TUI stability improvements

New features

- Background Processes Support - Added support for running and managing background processes in the CLI. Includes a new bg-process command to list, kill, and clean up processes, with persistent process state tracking.
- MCP Registry Search - Added search functionality to the MCP registry list view (/mcp). Filter available MCP servers by typing directly in the list interface.

Bug fixes

- Fixed race conditions and rendering issues when suspending/resuming the TUI (e.g., when opening an external editor).
- Fixed circular dependency issues in grep tool logging.