feat: explain_refresh_materialized_view over REST (EXPLAIN REFRESH SDK)

Database trait gains explain_refresh_materialized_view (default NotSupported)
returning an MvRefreshPlan; RemoteDatabase POSTs
/v1/materialized_view/{name}/explain_refresh; Connection method; pyo3
MvRefreshPlan pyclass + binding; sync+async python wrappers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

python/python/lancedb/db.py

@@ -642,6 +642,23 @@ class DBConnection(EnforceOverrides):
             )
         )
 
+    def explain_refresh_materialized_view(
+        self,
+        name: str,
+        *,
+        full: bool = False,
+        src_version: Optional[int] = None,
+    ):
+        """Plan a refresh without running it (EXPLAIN REFRESH). Returns a
+        plan with .has_work / .source_version / .last_refreshed_version /
+        .full_refresh / .rebuild / .units_total. `full=True` plans a full
+        rebuild (incremental planning needs stable row IDs on the source)."""
+        return LOOP.run(
+            self._conn.explain_refresh_materialized_view(
+                name, full=full, src_version=src_version
+            )
+        )
+
     def alter_materialized_view(self, name: str, *, auto_refresh: bool):
         """Update a materialized view's options (ALTER MATERIALIZED VIEW)."""
         LOOP.run(self._conn.alter_materialized_view(name, auto_refresh=auto_refresh))
@@ -1944,6 +1961,18 @@ class AsyncConnection(object):
             max_workers=max_workers,
         )
 
+    async def explain_refresh_materialized_view(
+        self,
+        name: str,
+        *,
+        full: bool = False,
+        src_version: Optional[int] = None,
+    ):
+        """Plan a refresh without running it (EXPLAIN REFRESH)."""
+        return await self._inner.explain_refresh_materialized_view(
+            name, full=full, src_version=src_version
+        )
+
     async def alter_materialized_view(self, name: str, *, auto_refresh: bool):
         """Update a materialized view's options."""
         await self._inner.alter_materialized_view(name, auto_refresh)