Implementation Plan

Done when: Fluid mode switching and scrolling feels vim-native

Parse command buffer on enter: :quit -> Quit, :clear -> clear messages and history, :q alias for :quit
Return appropriate LoopControl or mutate AppState directly for display-only commands
Unknown commands -> show error in a transient status area

Add a status bar row at the bottom of the layout (below input pane)
Status bar shows: current mode (-- NORMAL --, -- INSERT --), token totals (placeholder for now)
Style: bold, color-coded per mode (following vim convention)
Command input renders as a floating bar near the top of the screen (overlay on the output pane), not in the status bar
Command overlay: shows : prefix + partial command buffer, only visible in Command mode
Overlay dismisses on Esc or Enter

Normal mode: input pane shows last draft (unsent) message or is empty, not editable
Insert mode: input pane is editable (current behavior)
Command mode: floating overlay near top shows : prefix + command buffer; input pane unchanged
Cursor visibility: show cursor in Insert and Command modes, hide in Normal

Mode transitions: Normal->Insert->Normal, Normal->Command->Normal, Command execute
Key dispatch: correct handler called per mode
Command parser: :quit, :clear, :q, unknown command
Scroll clamping: j/k at boundaries, G/gg
insta snapshot tests: mode indicator rendering for each mode, layout with status bar
Existing Phase 1 input tests still pass (insert mode behavior unchanged)

Phase 3: Tool Execution

Tool trait, ToolRegistry, core tools (read_file, write_file, shell_exec)
Tool definitions in API requests, parse tool-use responses
Approval gate: core -> TUI pending event -> user approve/deny -> result back
Working directory confinement + path validation (no Landlock yet)
Done when: Claude can read, modify files, and run commands with user approval