fix(ruff): sort imports and use datetime.UTC alias in session_store

- Organize Python imports per ruff I001 rule
- Replace deprecated timezone.utc with datetime.UTC alias (UP017)
- Break long SQL string literal across multiple lines (E501)

src/cleveragents/tui/session_store.py

@@ -5,10 +5,9 @@ from __future__ import annotations
 import sqlite3
 import threading
 from dataclasses import dataclass, field
-from datetime import datetime, timezone
+from datetime import UTC, datetime
 from pathlib import Path
 
-
 ALLOWED_STATES = ("idle", "working", "awaiting_input")
 
 
@@ -26,7 +25,7 @@ class SessionRecord:
 
 def _utcnow() -> datetime:
     """Return the current UTC timestamp (timezone-aware)."""
-    return datetime.now(timezone.utc)
+    return datetime.now(UTC)
 
 
 class SessionStore:
@@ -233,7 +232,9 @@ class SessionStore:
             )
             try:
                 conn.execute(
-                    "UPDATE sessions SET state = ?, updated_at = ? WHERE session_id = ?",
+                    "UPDATE sessions SET "
+                    "state = ?, updated_at = ? "
+                    "WHERE session_id = ?",
                     (state, now.isoformat(), session_id),
                 )
                 conn.commit()