fix(sessions): pinned-skip note counts pinned rows, not spared ancestors

_note_pinned_skipped diffed count_prune_matches(include_pinned=True/False)
with whole_lineages on for prune. Excluding a pinned tip turns it into an
unmatched continuation, so its unpinned compression ancestors drop out of
the "without" count too and the note reported them as pinned (chain
a -> a-2 -> a-3 with only a-3 pinned said "3 pinned sessions").

Count plain filter matches for the note; the delete itself is unchanged.
count_prune_matches has no other caller that needs whole_lineages, so the
keyword goes back to base's signature.

hermes_state_maintenance.py

@@ -250,10 +250,10 @@ class SessionMaintenanceMixin:
                     FROM sessions s WHERE {where}
                     ORDER BY last_active ASC, s.started_at ASC""", params)]
 
-    def count_prune_matches(self, older_than_days: Optional[float] = None, source: str = None, *,
-                            whole_lineages: bool = False, **filters) -> int:
+    def count_prune_matches(self, older_than_days: Optional[float] = None, source: str = None,
+                            **filters) -> int:
         """Count-only :meth:`list_prune_candidates` (CLI reports spared pinned sessions)."""
-        where, params = self._prune_where(older_than_days, source, filters, whole_lineages=whole_lineages)
+        where, params = self._prune_where(older_than_days, source, filters)
         return int(self._read_one(f"SELECT COUNT(*) FROM sessions s WHERE {where}", params)[0])
 
     def count_open_prune_matches(self, older_than_days: Optional[float] = None, source: str = None, *,