feat(ecc2): add token/cost meter widget (#775)

- TokenMeter widget using ratatui Gauge with color gradient (green->yellow->red)
- Budget fields (cost_budget_usd, token_budget) in Config
- Aggregate cost display in status bar
- Warning state at 80%+ budget consumption
- Tests for gradient, config fallback, and meter rendering

ecc2/src/session/store.rs

@@ -236,7 +236,6 @@ impl StateStore {
             .into_iter()
             .find(|s| s.id == id || s.id.starts_with(id)))
     }
-
     pub fn send_message(&self, from: &str, to: &str, content: &str, msg_type: &str) -> Result<()> {
         self.conn.execute(
             "INSERT INTO messages (from_session, to_session, content, msg_type, timestamp)