fix(searcher): guard against None metadata in CLI print path

`col.query(...)` can return `None` entries in the inner ``metadatas`` list
for drawers whose metadata was never set (older palaces, rows written
outside the normal mining path). The CLI `search()` function would render
earlier results successfully and then crash mid-loop with:

    AttributeError: 'NoneType' object has no attribute 'get'

at ``searcher.py:286`` — ``meta.get("source_file", "?")``. The user sees
partial output followed by a traceback, with no indication of which
drawers rendered OK and which were skipped.

Guard with ``meta = meta or {}`` inside the loop so entries with missing
metadata fall back to the existing ``"?"`` defaults instead of crashing,
matching the hit dict assembly in ``search_memories()`` which already
uses ``meta.get("wing", "unknown")`` etc. against the same data.

Adds a regression test that mocks a ChromaDB result with a ``None``
metadata entry in the middle of the inner list and asserts both result
blocks render to stdout.

tests/test_searcher.py

@@ -141,3 +141,22 @@ class TestSearchCLI:
         captured = capsys.readouterr()
         # Should have output with at least one result block
         assert "[1]" in captured.out
+
+    def test_search_handles_none_metadata_without_crash(self, palace_path, capsys):
+        """ChromaDB can return `None` entries in the metadatas list when a
+        drawer has no metadata. The CLI print path must not crash on them
+        mid-render — it used to raise `AttributeError: 'NoneType' object has
+        no attribute 'get'` after printing earlier results."""
+        mock_col = MagicMock()
+        mock_col.query.return_value = {
+            "documents": [["first doc", "second doc"]],
+            "metadatas": [[{"source_file": "a.md", "wing": "w", "room": "r"}, None]],
+            "distances": [[0.1, 0.2]],
+        }
+        with patch("mempalace.searcher.get_collection", return_value=mock_col):
+            search("anything", "/fake/path")
+        captured = capsys.readouterr()
+        assert "[1]" in captured.out
+        assert "[2]" in captured.out
+        # Second result renders with fallback '?' values instead of crashing
+        assert "second doc" in captured.out