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/worktree/mod.rs

@@ -0,0 +1,80 @@
+use anyhow::{Context, Result};
+use std::path::PathBuf;
+use std::process::Command;
+
+use crate::config::Config;
+use crate::session::WorktreeInfo;
+
+/// Create a new git worktree for an agent session.
+pub fn create_for_session(session_id: &str, cfg: &Config) -> Result<WorktreeInfo> {
+    let branch = format!("ecc/{session_id}");
+    let path = cfg.worktree_root.join(session_id);
+
+    // Get current branch as base
+    let base = get_current_branch()?;
+
+    std::fs::create_dir_all(&cfg.worktree_root)
+        .context("Failed to create worktree root directory")?;
+
+    let output = Command::new("git")
+        .args(["worktree", "add", "-b", &branch])
+        .arg(&path)
+        .arg("HEAD")
+        .output()
+        .context("Failed to run git worktree add")?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        anyhow::bail!("git worktree add failed: {stderr}");
+    }
+
+    tracing::info!("Created worktree at {} on branch {}", path.display(), branch);
+
+    Ok(WorktreeInfo {
+        path,
+        branch,
+        base_branch: base,
+    })
+}
+
+/// Remove a worktree and its branch.
+pub fn remove(path: &PathBuf) -> Result<()> {
+    let output = Command::new("git")
+        .args(["worktree", "remove", "--force"])
+        .arg(path)
+        .output()
+        .context("Failed to remove worktree")?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        tracing::warn!("Worktree removal warning: {stderr}");
+    }
+
+    Ok(())
+}
+
+/// List all active worktrees.
+pub fn list() -> Result<Vec<String>> {
+    let output = Command::new("git")
+        .args(["worktree", "list", "--porcelain"])
+        .output()
+        .context("Failed to list worktrees")?;
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let worktrees: Vec<String> = stdout
+        .lines()
+        .filter(|l| l.starts_with("worktree "))
+        .map(|l| l.trim_start_matches("worktree ").to_string())
+        .collect();
+
+    Ok(worktrees)
+}
+
+fn get_current_branch() -> Result<String> {
+    let output = Command::new("git")
+        .args(["rev-parse", "--abbrev-ref", "HEAD"])
+        .output()
+        .context("Failed to get current branch")?;
+
+    Ok(String::from_utf8_lossy(&output.stdout).trim().to_string())
+}