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/config/mod.rs

@@ -0,0 +1,54 @@
+use anyhow::Result;
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Config {
+    pub db_path: PathBuf,
+    pub worktree_root: PathBuf,
+    pub max_parallel_sessions: usize,
+    pub max_parallel_worktrees: usize,
+    pub session_timeout_secs: u64,
+    pub heartbeat_interval_secs: u64,
+    pub default_agent: String,
+    pub theme: Theme,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum Theme {
+    Dark,
+    Light,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        let home = dirs::home_dir().unwrap_or_else(|| PathBuf::from("."));
+        Self {
+            db_path: home.join(".claude").join("ecc2.db"),
+            worktree_root: PathBuf::from("/tmp/ecc-worktrees"),
+            max_parallel_sessions: 8,
+            max_parallel_worktrees: 6,
+            session_timeout_secs: 3600,
+            heartbeat_interval_secs: 30,
+            default_agent: "claude".to_string(),
+            theme: Theme::Dark,
+        }
+    }
+}
+
+impl Config {
+    pub fn load() -> Result<Self> {
+        let config_path = dirs::home_dir()
+            .unwrap_or_else(|| PathBuf::from("."))
+            .join(".claude")
+            .join("ecc2.toml");
+
+        if config_path.exists() {
+            let content = std::fs::read_to_string(&config_path)?;
+            let config: Config = toml::from_str(&content)?;
+            Ok(config)
+        } else {
+            Ok(Config::default())
+        }
+    }
+}