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/session/manager.rs

@@ -0,0 +1,76 @@
+use anyhow::Result;
+use std::fmt;
+
+use super::{Session, SessionMetrics, SessionState};
+use super::store::StateStore;
+use crate::config::Config;
+use crate::worktree;
+
+pub async fn create_session(
+    db: &StateStore,
+    cfg: &Config,
+    task: &str,
+    agent_type: &str,
+    use_worktree: bool,
+) -> Result<String> {
+    let id = uuid::Uuid::new_v4().to_string()[..8].to_string();
+    let now = chrono::Utc::now();
+
+    let wt = if use_worktree {
+        Some(worktree::create_for_session(&id, cfg)?)
+    } else {
+        None
+    };
+
+    let session = Session {
+        id: id.clone(),
+        task: task.to_string(),
+        agent_type: agent_type.to_string(),
+        state: SessionState::Pending,
+        worktree: wt,
+        created_at: now,
+        updated_at: now,
+        metrics: SessionMetrics::default(),
+    };
+
+    db.insert_session(&session)?;
+    Ok(id)
+}
+
+pub fn list_sessions(db: &StateStore) -> Result<Vec<Session>> {
+    db.list_sessions()
+}
+
+pub fn get_status(db: &StateStore, id: &str) -> Result<SessionStatus> {
+    let session = db
+        .get_session(id)?
+        .ok_or_else(|| anyhow::anyhow!("Session not found: {id}"))?;
+    Ok(SessionStatus(session))
+}
+
+pub async fn stop_session(db: &StateStore, id: &str) -> Result<()> {
+    db.update_state(id, &SessionState::Stopped)?;
+    Ok(())
+}
+
+pub struct SessionStatus(Session);
+
+impl fmt::Display for SessionStatus {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = &self.0;
+        writeln!(f, "Session: {}", s.id)?;
+        writeln!(f, "Task:    {}", s.task)?;
+        writeln!(f, "Agent:   {}", s.agent_type)?;
+        writeln!(f, "State:   {}", s.state)?;
+        if let Some(ref wt) = s.worktree {
+            writeln!(f, "Branch:  {}", wt.branch)?;
+            writeln!(f, "Worktree: {}", wt.path.display())?;
+        }
+        writeln!(f, "Tokens:  {}", s.metrics.tokens_used)?;
+        writeln!(f, "Tools:   {}", s.metrics.tool_calls)?;
+        writeln!(f, "Files:   {}", s.metrics.files_changed)?;
+        writeln!(f, "Cost:    ${:.4}", s.metrics.cost_usd)?;
+        writeln!(f, "Created: {}", s.created_at)?;
+        write!(f, "Updated: {}", s.updated_at)
+    }
+}