Add modal editing to the agent TUI. (#2)

Adds a status line indicating which mode the user is in.
Adds a "normal" mode with keyboard shortcuts (including a chorded shortcut 'gg').
Adds a command mode with several basic commands that can be entered into an overlay.

Chores:
- Cleans up design/claude/plan.md to avoid confusing claude.
- Adds some TODOs based on claude feedback.`

Reviewed-on: #2
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

PLAN.md

@@ -1,77 +1,9 @@
 # Implementation Plan
 
-## Phase 1: Minimal Conversation Loop
-
-**Done when:** Multi-turn streaming conversation with Claude works in terminal
-
-### 1.1 Project Scaffolding
-- `Cargo.toml` with initial dependencies:
-  - `ratatui`, `crossterm` — TUI
-  - `tokio` (full features) — async runtime
-  - `serde`, `serde_json` — serialization
-  - `thiserror` — error types
-  - `tracing`, `tracing-subscriber` — structured logging
-  - `reqwest` (with `stream` feature) — HTTP client for SSE
-  - `futures` — stream combinators
-- Establish `src/{app,tui,core,provider}/mod.rs` stubs
-- `cargo build` passes; `cargo clippy -- -D warnings` passes on empty stubs
-
-### 1.2 Shared Types (`src/core/types.rs`)
-- `StreamEvent` enum: `TextDelta(String)`, `InputTokens(u32)`, `OutputTokens(u32)`, `Done`, `Error(String)`
-- `UserAction` enum (TUI → core channel): `SendMessage(String)`, `Quit`
-- `UIEvent` enum (core → TUI channel): `StreamDelta(String)`, `TurnComplete`, `Error(String)`
-- `ConversationMessage` struct: `role: Role`, `content: String`
-- All types derive `Debug`; all public types have doc comments
-
-### 1.3 Provider: `ModelProvider` Trait + Claude SSE (`src/provider/`)
-- `ModelProvider` trait: `async fn stream(&self, messages: &[ConversationMessage]) -> impl Stream<Item = StreamEvent>`
-- `ClaudeProvider` struct: API key from env, `reqwest` HTTP client
-- Serialize messages to Anthropic Messages API JSON format
-- Parse SSE byte stream → `StreamEvent` (handle `content_block_delta`, `message_delta` for tokens, `message_stop`)
-- Unit tests: SSE parsing from hardcoded byte fixtures in `#[cfg(test)]`
-
-### 1.4 Core: Conversation State + Orchestrator Loop (`src/core/`)
-- `ConversationHistory`: `Vec<ConversationMessage>` with `push` and `messages()` (flat list, no tree yet)
-- `Orchestrator` struct holding history, provider, channel senders/receivers
-- Orchestrator loop:
-  1. Await `UserAction` from TUI channel
-  2. On `SendMessage`: append user message, call `provider.stream()`
-  3. Forward each `StreamEvent` as `UIEvent` to TUI
-  4. Accumulate deltas into assistant message; append to history on `Done`
-  5. On `Quit`: break loop
-
-### 1.5 TUI: Layout + Input + Streaming Display (`src/tui/`)
-- `AppState` struct: `messages: Vec<(Role, String)>`, `input: String`, `scroll: u16`
-- Ratatui layout: full-height `Paragraph` output area (scrollable) + single-line `Paragraph` input
-- Insert mode only — printable chars append to `input`, Enter sends `UserAction::SendMessage`, Backspace deletes
-- On `UIEvent::StreamDelta`: append to last assistant message in `messages`, re-render
-- On `UIEvent::TurnComplete`: finalize assistant message
-- Crossterm raw mode enter/exit; restore terminal on panic or clean exit
-
-### 1.6 App Wiring + Entry Point (`src/app/`, `src/main.rs`)
-- `main.rs`: parse `--project-dir <path>` CLI arg
-- Initialize `tracing_subscriber` (log to file, not stdout — avoids TUI interference)
-- Create `tokio::sync::mpsc` channel pair for `UserAction` and `UIEvent`
-- Spawn `Orchestrator::run()` as a tokio task
-- Run TUI event loop on main thread (Ratatui requires main thread for crossterm)
-- On `UserAction::Quit` or Ctrl-C: signal orchestrator shutdown, restore terminal, exit cleanly
-
-### 1.7 Phase 1 Unit Tests
-- Provider: SSE byte fixture → correct `StreamEvent` sequence
-- Provider: `ConversationMessage` vec → correct Anthropic API JSON shape
-- Core: `ConversationHistory` push/read roundtrip
-- Core: Orchestrator state transitions against mock `StreamEvent` sequence (no real API)
-
-## Phase 2: Vim Modes and Navigation
-- Normal, Insert, Command modes with visual indicator
-- `j`/`k` scroll in Normal mode
-- `:quit`, `:clear` commands
-- **Done when:** Fluid mode switching and scrolling feels vim-native
-
 ## 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
+- 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
 
@@ -81,8 +13,3 @@
 - `:net on/off` toggle, state in status bar
 - Graceful degradation on older kernels
 - **Done when:** Writes outside project dir fail; network toggle works
-
-
-
-
-