perf(state): counters from the rows in hand, bounded identity read, one row-identity helper

Efficiency gate: replace_messages had swapped the free insert-return counters for a full
active-set rescan (JSON parse per row) on every branch, slowing the untouched compress/ACP
path; the counts are now kept-prefix (from the fetched rows) + inserted. The identity SELECT
is bounded to len(messages)+1 rows — the prefix plus the row that anchors the archive UPDATE.
_row_identity is the one place the compared columns are spelled; _kept_live_prefix became
_stamp_kept_live_prefix (it mutates _row_id); rewind's _comparison_content delegates to the
shared _loaded_view_content.

hermes_state_rewind.py

@@ -34,12 +34,9 @@ def _user_indices(messages: List[Dict[str, Any]]) -> List[int]:
 def _comparison_content(message: Dict[str, Any]) -> Any:
     """Project content the way the durable row stores it (flush projection, then the read-side sanitize) so a
     warm row and its durable twin compare equal."""
-    from agent.memory_manager import sanitize_context
     from agent.session_persistence import _durable_content
-    content = _durable_content(message.get("content"))
-    if message.get("role") in {"user", "assistant"} and isinstance(content, str):
-        return sanitize_context(content).strip()
-    return content
+    from hermes_state_messages import SessionMessagesMixin
+    return SessionMessagesMixin._loaded_view_content(message.get("role"), _durable_content(message.get("content")))
 
 
 class SessionRewindMixin: