Answer the review, and keep the opening node's bank

Nine findings from a review of the phase-14 stack. The one about a retry
withdrawing a memory is not a bug — a memory anchored to a node describes that
node, and it goes when the node goes. The root is the exception, and it is the
only one: migration 62 parked every memory written before memories had
coordinates on depth 0, so withdrawing the opening node would retire a whole
bank nobody attached there. A memory with no source range covers no story and
now stays; a summary that genuinely ends there is still withdrawn.

The rest are repairs.

* The adventure list quoted whichever attempt was written last rather than the
  one the story tells, so switching back left the index disagreeing with the
  page.
* A v1 import gave a typed memory no depth, rebuilding the NULL the migration
  exists to remove — invisible until the imported adventure forked.
* The action cap counted a v1 file's turns, and a turn expands into a row per
  saved attempt, so a file inside the cap could write a multiple of it.
* Forking a live node on a borrowed ancestor promoted a sibling on a branch the
  caller never named. It is a branch switch, and now says so.
* Switching attempts left the state, status and memory panels reading the
  previous take: the story does not change length, so nothing keyed on its
  length noticed. Same class as the branch-switch bug this phase already fixed.
* A retry after switching back numbered the new attempt into the middle of the
  group instead of the end.
* The cursor backfill numbered every action in the table once per adventure;
  correlated to the adventure being updated, it is an index lookup instead.
* Renaming a branch answered own_actions=0.

And one behaviour change recorded rather than repaired: script-visible history
and actionCount no longer count blank-text rows. That is the right shape and
there is no reading compatible with both, so plan/14 says so.

409 tests.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015H5qiyiR7gtFQaoDphHZ3g

backend/tests/test_memory_nodes.py

@@ -452,3 +452,53 @@ def test_retrieving_from_a_deep_fork_costs_what_a_flat_story_costs(deeply_forked
         f"retrieval on a 20-fork story cost {forked_bytes:,} B against the "
         f"{flat_bytes:,} B a flat story of the same length cost"
     )
+
+
+# ------------------------------------------------------- the opening node
+
+def test_a_typed_memory_on_the_opening_node_survives_that_node_going(forked):
+    """The one place a node and its memories part company.
+
+    A memory anchored to a node is withdrawn with the node, which is the rule
+    and is deliberate: it described that turn, and the turn is leaving. But
+    migration 62 parked *every* memory written before memories had coordinates
+    on depth 0 — the only landing spot visible from every branch — so the
+    opening node carries a whole bank it never produced. Withdrawing it would
+    retire all of that in one click, for every adventure predating the tree.
+
+    A memory with no `source_start` covers no stretch of story, so nothing about
+    it can go stale. It stays.
+    """
+    db, adventure, settings, ids = forked
+    typed = models.Memory(
+        adventure_id=adventure.id, text="Kira is the innkeeper's daughter",
+        source_start=None, source_end=None,
+    )
+    typed.branch_id, typed.depth = ids["a"], 0
+    db.add(typed)
+    db.commit()
+    typed_id = typed.id
+
+    withdrawn = memorybank.forget_node(db, adventure, ids["nodes"]["A0"])
+    db.commit()
+
+    assert withdrawn == 0
+    assert db.get(models.Memory, typed_id) is not None
+
+
+def test_a_summary_of_the_opening_node_is_still_withdrawn(forked):
+    """The exception is about memories that describe nothing, not about depth 0.
+
+    A summary that genuinely ends on the opening node describes text that is
+    going, so it goes too — otherwise the root would collect exactly the
+    dangling rows `forget_node` replaced `prune_dangling_memories` to prevent.
+    """
+    db, adventure, settings, ids = forked
+    derived = add_memory(db, adventure, "the opening, summarised", ids["nodes"]["A0"])
+    derived_id = derived.id
+
+    withdrawn = memorybank.forget_node(db, adventure, ids["nodes"]["A0"])
+    db.commit()
+
+    assert withdrawn == 1
+    assert db.get(models.Memory, derived_id) is None