fix: improve invalid command handling and UI consistency

refactor: clean up UI manager with extracted helpers and improved docs

fix: UI spacing improvements and bug fixes

test: update tests for refactored UI API

fix: UI spacing consistency issues

fix: UI spacing issues with error handling and user input

refactor: simplify UI system with centralized state management

feat: Add cancellation context to message history on Ctrl+C

fix: interrupt MCP server requests with single Ctrl+C

refactor: Extract message history from Session to dedicated MessageHistory class

refactor: Move interrupt handling from Session to Repl class

fix: update system prompt to match actual available tools

refactor: Extract usage tracking from Session into dedicated UsageTracker

refactor: Extract common subprocess logic in find.py to reduce duplication

refactor: Consolidate grep and find tools into single unified tool