fix(surprisal): use correct filter format for level observations (#581)

The Surprisal module passes `{"level": levels}` directly to
`get_all_documents()`, but `apply_filter()` expects operator syntax:
`{"level": {"in": levels}}`.

Without the `in` operator, the filter is silently ignored, causing
`_fetch_level_observations()` to return 0 results. This makes the
entire Surprisal phase of the Dream cycle a no-op.

Fixes #559

src/dreamer/surprisal.py

@@ -261,7 +261,7 @@ async def _fetch_recent_observations(
         workspace_name=workspace_name,
         observer=observer,
         observed=observed,
-        filters={"level": levels} if levels else None,
+        filters={"level": {"in": levels}} if levels else None,
         limit=limit,
     )