feat(6243): a directory moved in the tree keeps its shape judgments

Ledger rows are keyed by path, so after a directory moves the next sync
marks every judged row vanished and lists the same shapes again, unjudged.
move_shapes(project_id, from_path, to_path) re-keys the rows under one path
to the other, in every repo of the project, keeping each row's judgment,
uses edges and history and adding a `moved` event that records the path it
left. A row already at the target is replaced when nobody judged it; a
judged one stands, and the old row is reported in `kept`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_shape_ledger.py

@@ -642,5 +642,5 @@ def test_history_and_divergence_columns_are_pinned():
     fk = next(iter(ev.c.shape_id.foreign_keys))
     assert fk.ondelete == "CASCADE" and fk.column.table.name == "code_shapes"
     assert not ev.c.snippet_id.foreign_keys           # history outlives the snippet
-    assert SHAPE_EVENTS == ("classified", "vanished", "reappeared", "drifted")
+    assert SHAPE_EVENTS == ("classified", "vanished", "reappeared", "drifted", "moved")
     assert "code_shape_events" in Base.metadata.tables