Drop the eight legacy columns SP8 left behind

Migrations 66 to 73 drop `actions.index`, `variants`, `variant_index`,
`variant_count`, `state_before`, and `world_state_before`, plus
`adventures.memory_cursor` and `summary_cursor`. `index` is a keyword in
SQLite, so migration 71 quotes it.

Nothing outside the migrations read these. `models.py`, `schemas.py`, and
`ACTION_LIST_COLUMNS` lose the same eight fields, `Adventure.actions` orders
by `id`, and `attempts.renumber`, `context.history.max_action_index`, and
`nodes.next_index` are deleted.

Two changes keep the migration replayable on a `create_all` database:

- `_split_variants_into_siblings` wrote through the live ORM table, so it
  stopped compiling once migration 66 removed five of its columns. It now
  writes through `_ACTIONS_AT_60`, a frozen `Table` with its own `MetaData`.
- Five data passes read columns these migrations drop. Each now calls
  `_has_columns` and returns early when the columns are absent.

`bootstrap` takes a `through` version so a migration test can stop at the
schema it asserts on.

555 tests pass, up from 549. Eight of the new cases assert each column is
gone after a real schema-45 database migrates all the way.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0198qDK3gmgSo7EtQ4GTPqqK

backend/tests/test_attempt_siblings.py

@@ -49,7 +49,7 @@ def client(monkeypatch):
     )
     setup.add(adv)
     setup.flush()
-    setup.add(models.Action(adventure_id=adv.id, index=0, type="start", text="You enter a cave."))
+    setup.add(models.Action(adventure_id=adv.id, type="start", text="You enter a cave."))
     setup.add(models.AdventureScript(
         adventure_id=adv.id, position=0, enabled=True, name="Gold", output_js=GOLD_SCRIPT,
     ))
@@ -112,7 +112,7 @@ def _rows(adv_id) -> list[models.Action]:
                 undefer(models.Action.world_state_after),
                 undefer(models.Action.context_snapshot),
             )
-            .order_by(models.Action.depth, models.Action.variant_index)
+            .order_by(models.Action.depth, models.Action.id)
             .all()
         )
     finally:
@@ -330,16 +330,22 @@ def test_a_memory_on_an_earlier_turn_survives_a_retry(client):
 
 # -------------------------------------------------------------- the group
 
-def test_the_group_cache_is_renumbered_as_attempts_arrive(client):
+def test_the_group_grows_in_the_order_the_attempts_arrive(client):
+    """The attempts page in the order they were made, and the pager counts them.
+
+    Ordering used to come from `variant_index`, an explicit ordinal that SP8
+    dropped. `id` carries the same order, because a row is inserted when its
+    attempt is made.
+    """
     ScriptedProvider.replies = ["One.", "Two.", "Three."]
     _play(client)
-    assert _page(client)["actions"][-1]["variant_count"] == 0  # never retried
+    assert _page(client)["actions"][-1]["take_count"] == 1  # never retried
     _retry(client)
     _retry(client)
 
     ai = [a for a in _rows(client.adv_id) if a.type == "ai"]
-    assert [a.variant_index for a in ai] == [0, 1, 2]
-    assert {a.variant_count for a in ai} == {3}
+    assert [a.text for a in ai] == ["One.", "Two.", "Three."]
+    assert _page(client)["actions"][-1]["take_count"] == 3
 
 
 def test_attempts_module_agrees_with_the_endpoint(client):
@@ -394,9 +400,8 @@ def test_a_retry_after_switching_back_files_the_new_attempt_last(client):
     `add_attempt` used to number a new take one past the take it replaced.
     That numbering is correct only when the story is standing on the newest
     take. Switch a three-take turn back to the first and retry, and the new
-    attempt collides with take 2. `renumber` broke the tie by id and placed
-    the new attempt between takes 2 and 3, so the pager listed them in an
-    order the player never produced.
+    attempt collided with take 2, which put it between takes 2 and 3. The
+    group orders by `id` now, so a new attempt is always last.
     """
     ScriptedProvider.replies = ["One.", "Two.", "Three.", "Four."]
     _play(client)
@@ -414,7 +419,6 @@ def test_a_retry_after_switching_back_files_the_new_attempt_last(client):
     _retry(client)
     ai = [a for a in _rows(client.adv_id) if a.type == "ai"]
     assert [a.text for a in ai] == ["One.", "Two.", "Three.", "Four."]
-    assert [a.variant_index for a in ai] == [0, 1, 2, 3]
     assert attempts.live_in(ai).text == "Four."