feat: scaffold ECC 2.0 Rust TUI — agentic IDE control plane

Initial scaffold for ECC 2.0, a terminal-native agentic IDE built with
Ratatui. Compiles to a 3.4MB single binary.

Core modules:
- Session manager with SQLite-backed state store
- TUI dashboard with split-pane layout (sessions, output, metrics)
- Worktree orchestration (auto-create per agent session)
- Observability with tool call risk scoring
- Inter-agent communication via SQLite mailbox
- Background daemon with heartbeat monitoring
- CLI with start/stop/sessions/status/daemon subcommands

Tech stack: Rust + Ratatui + Crossterm + Tokio + rusqlite + git2 + clap

ecc2/src/tui/app.rs

@@ -0,0 +1,52 @@
+use anyhow::Result;
+use crossterm::{
+    event::{self, Event, KeyCode, KeyModifiers},
+    execute,
+    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
+};
+use ratatui::prelude::*;
+use std::io;
+use std::time::Duration;
+
+use super::dashboard::Dashboard;
+use crate::config::Config;
+use crate::session::store::StateStore;
+
+pub async fn run(db: StateStore, cfg: Config) -> Result<()> {
+    enable_raw_mode()?;
+    let mut stdout = io::stdout();
+    execute!(stdout, EnterAlternateScreen)?;
+
+    let backend = CrosstermBackend::new(stdout);
+    let mut terminal = Terminal::new(backend)?;
+
+    let mut dashboard = Dashboard::new(db, cfg);
+
+    loop {
+        terminal.draw(|frame| dashboard.render(frame))?;
+
+        if event::poll(Duration::from_millis(250))? {
+            if let Event::Key(key) = event::read()? {
+                match (key.modifiers, key.code) {
+                    (KeyModifiers::CONTROL, KeyCode::Char('c')) => break,
+                    (_, KeyCode::Char('q')) => break,
+                    (_, KeyCode::Tab) => dashboard.next_pane(),
+                    (KeyModifiers::SHIFT, KeyCode::BackTab) => dashboard.prev_pane(),
+                    (_, KeyCode::Char('j')) | (_, KeyCode::Down) => dashboard.scroll_down(),
+                    (_, KeyCode::Char('k')) | (_, KeyCode::Up) => dashboard.scroll_up(),
+                    (_, KeyCode::Char('n')) => dashboard.new_session(),
+                    (_, KeyCode::Char('s')) => dashboard.stop_selected(),
+                    (_, KeyCode::Char('r')) => dashboard.refresh(),
+                    (_, KeyCode::Char('?')) => dashboard.toggle_help(),
+                    _ => {}
+                }
+            }
+        }
+
+        dashboard.tick().await;
+    }
+
+    disable_raw_mode()?;
+    execute!(terminal.backend_mut(), LeaveAlternateScreen)?;
+    Ok(())
+}