fix: _decay_edges — handle string updated_at from Qdrant and add TableShim delete/update

The Qdrant _TableShim returned updated_at as ISO strings (not datetime
objects), causing str.replace(tzinfo=...) to fail with
"str.replace() takes no keyword arguments". Parse strings via
datetime.fromisoformat() before timezone handling.

Also add missing delete(where) and update(where=, values=) methods to
_TableShim so the LanceDB-compatible shim works with Qdrant's payload
collection, plus a _parse_where() helper to convert where clauses to
Qdrant Filters.

src/iai_mcp/sleep.py

@@ -185,10 +185,13 @@ def _decay_edges(
             last = row["updated_at"]
             if last is None:
                 continue
-            # Coerce naive -> UTC; pandas may drop tz on some backends.
-            try:
-                py = last.to_pydatetime() if hasattr(last, "to_pydatetime") else last
-            except Exception:
+            # Coerce to datetime: pandas Timestamp -> pydatetime, ISO string -> datetime,
+            # or already a datetime object.
+            if hasattr(last, "to_pydatetime"):
+                py = last.to_pydatetime()
+            elif isinstance(last, str):
+                py = datetime.fromisoformat(last)
+            else:
                 py = last
             if getattr(py, "tzinfo", None) is None:
                 py = py.replace(tzinfo=timezone.utc)