chore(tui): keep MRU resume split out of perf PR

- remove the temporary -c MRU logic and companion test from this branch so PR #15926 stays focused on TUI perf work
- keep the resume-ordering change isolated in the dedicated follow-up PR

hermes_cli/main.py

@@ -596,32 +596,15 @@ def _session_browse_picker(sessions: list) -> Optional[str]:
 
 
 def _resolve_last_session(source: str = "cli") -> Optional[str]:
-    """Look up the most recently *used* session ID for a source.
-
-    Previously this returned the most recently *started* session, which meant
-    `hermes -c` could skip the session you just closed if a newer one had been
-    opened earlier in a different window. We now order by last_active
-    (max message timestamp, falling back to started_at) so -c always resumes
-    the most recent conversation you actually touched.
-    """
+    """Look up the most recent session ID for a source."""
     try:
         from hermes_state import SessionDB
 
         db = SessionDB()
-        sessions = db.search_sessions(source=source, limit=20)
+        sessions = db.search_sessions(source=source, limit=1)
         db.close()
-        if not sessions:
-            return None
-
-        def _last_active(s: dict) -> float:
-            v = s.get("last_active") or s.get("started_at") or 0
-            try:
-                return float(v)
-            except (TypeError, ValueError):
-                return 0.0
-
-        sessions.sort(key=_last_active, reverse=True)
-        return sessions[0]["id"]
+        if sessions:
+            return sessions[0]["id"]
     except Exception:
         pass
     return None