refactor(memory): promote on_session_reset to base provider hook

Replace hasattr-forked OpenViking-specific paths with a proper base-class
hook. Collapse the two agent wrappers into a single rotate_memory_session
so callers don't orchestrate commit + rebind themselves.

- MemoryProvider: add on_session_reset(new_session_id) as a default no-op
- MemoryManager: on_session_reset fans out unconditionally (no hasattr,
  no builtin skip — base no-op covers it)
- OpenViking: rename reset_session -> on_session_reset; drop the explicit
  POST /api/v1/sessions (OV auto-creates on first message) and the two
  debug raise_for_status wrappers
- AIAgent: collapse commit_memory_session + reinitialize_memory_session
  into rotate_memory_session(new_sid, messages)
- cli.py / run_agent.py: replace hasattr blocks and the split calls with
  a single unconditional rotate_memory_session call; compression path
  now passes the real messages list instead of []
- tests: align with on_session_reset, assert reset does NOT POST /sessions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

run_agent.py

@@ -3040,33 +3040,17 @@ class AIAgent:
             except Exception:
                 pass
     
-    def commit_memory_session(self, messages: list = None) -> None:
-        """Commit external memory providers for the current session.
-
-        Calls on_session_end() WITHOUT shutting down providers — the session
-        data (e.g. OpenViking) is committed for extraction, but the HTTP
-        client and provider state remain alive for the next session.
-        Called before session_id changes (e.g. /new, context compression).
-        """
-        if self._memory_manager:
-            try:
-                self._memory_manager.on_session_end(messages or [])
-            except Exception:
-                pass
-
-    def reinitialize_memory_session(self, new_session_id: str) -> None:
-        """Transition memory providers to a new session after commit.
-
-        Calls restart_session() which uses reset_session() on providers that
-        support it (cheap: keeps HTTP client, resets per-session counters) or
-        falls back to initialize() for providers that don't.
-        Called after session_id has been assigned (e.g. /new, compression).
-        """
-        if self._memory_manager:
-            try:
-                self._memory_manager.restart_session(new_session_id)
-            except Exception:
-                pass
+    def rotate_memory_session(self, new_session_id: str, messages: list = None) -> None:
+        """Commit the current memory session, then rebind providers to
+        new_session_id. Keeps HTTP clients/state alive across the transition.
+        Called when session_id rotates (e.g. /new, context compression)."""
+        if not self._memory_manager:
+            return
+        try:
+            self._memory_manager.on_session_end(messages or [])
+            self._memory_manager.on_session_reset(new_session_id)
+        except Exception:
+            pass
 
     def close(self) -> None:
         """Release all resources held by this agent instance.
@@ -6854,14 +6838,11 @@ class AIAgent:
             try:
                 # Propagate title to the new session with auto-numbering
                 old_title = self._session_db.get_session_title(self.session_id)
-                # Commit external memory (e.g. OpenViking) before session_id
-                # changes so extraction runs on the correct session.
-                self.commit_memory_session([])
                 self._session_db.end_session(self.session_id, "compression")
                 old_session_id = self.session_id
                 self.session_id = f"{datetime.now().strftime('%Y%m%d_%H%M%S')}_{uuid.uuid4().hex[:6]}"
-                # Transition external memory providers to the new session_id.
-                self.reinitialize_memory_session(self.session_id)
+                # Commit the old memory session and rebind providers to the new one.
+                self.rotate_memory_session(self.session_id, messages)
                 # Update session_log_file to point to the new session's JSON file
                 self.session_log_file = self.logs_dir / f"session_{self.session_id}.json"
                 self._session_db.create_session(