fix(tests): provisional ledger rows carry the empty seen-marker default, not NULL

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/services/shape_ledger.py

@@ -512,7 +512,7 @@ async def stamp_write_path_instances(
     {path, symbol, kind, snippet_id, reason} — empty in the common case.
 
     A shape the ledger has no live row for yet (it is being written right
-    now) gets a PROVISIONAL row under ``repo_key`` — first/last-seen unset —
+    now) gets a PROVISIONAL row under ``repo_key`` — first/last-seen empty —
     so the stamp is not lost to the next sync, which either confirms the
     shape (sets its seen marker) or stamps it vanished. No repo key → only
     existing rows are stamped.

tests/test_integration_shape_classify.py

@@ -284,7 +284,7 @@ async def test_write_path_stamp_is_evidence_that_yields_to_judgment(seeded):
 @pytest.mark.integration
 async def test_a_brand_new_shape_gets_a_provisional_row_the_sync_settles(seeded):
     """The shape being written right now has no ledger row yet. With the
-    hook's repo key it gets a provisional one — seen markers unset — so the
+    hook's repo key it gets a provisional one — seen markers empty — so the
     stamp survives until the next sync, which confirms it (sets the marker)
     or stamps it vanished. Without a repo key only existing rows are touched."""
     from datetime import datetime, timezone
@@ -309,7 +309,9 @@ async def test_a_brand_new_shape_gets_a_provisional_row_the_sync_settles(seeded)
             CodeShape.project_id == pid, CodeShape.path == "src/new.py",
         ))).scalar_one()
         assert row.status == "instance" and row.classified_by == "hook"
-        assert row.first_seen_commit is None and row.last_seen_commit is None
+        # "Unset" is the column's empty default — the markers are non-null
+        # Text, and the sync is what first fills them.
+        assert row.first_seen_commit == "" and row.last_seen_commit == ""
 
     # The sync sees the shape in the tree → confirmed, stamp intact.
     await sync_repo_shapes(