M5: genre-neutral authoritative narrative state, with review corrections

Replaces AI-DnD's RPG relative-delta world state with the genre-neutral typed
narrative state of ADR 010: explicit, absolute, allowlisted events proposed by
the model, validated by the application, applied to one authoritative document,
and snapshotted per position so restore stays a row read.

This commit includes the corrective pass that followed the independent review
in planning/reports/M5-IMPLEMENTATION-REPORT.md. The invariant it exists to
hold is:

    visible active transcript position == stored head == authoritative state

Narrator editing (D10, STORY-BRANCH-SEMANTICS §§14-15)

  A narrator edit no longer rewrites a row. It returns to the state before the
  turn, takes the reader's exact text as the accepted narration, re-derives the
  state that text implies, and becomes a new active continuation — while the
  original narration keeps its words, its live flag and its whole future as
  retained history. At the tip the correction is another take; with story below
  it, it forks. No new history machinery: this is the existing fork/take/head
  path with the reader's text in place of a generated reply. The §14A refusal
  is therefore gone for narrator turns, and remains only for player input.

Pre-M5 positions

  Migration 88 backfills the empty narrative document onto every action written
  before M5, and a missing snapshot now restores the empty document instead of
  leaving the previous position's state standing. Restoring to an old Save
  Point no longer leaves a later position's entities and facts on screen.

Narrator context

  Replayed history carries prose only; the machine-readable block is no longer
  reconstructed into past turns, where it contradicted the authoritative state
  in the same prompt. A fact withdrawn by a manual correction is now named as
  no longer true, with the reader's reason, rather than silently dropped.

Also

  - state_changes joins the action-list bulk read, removing one query per row.
  - Extraction takes only the application's own protocol payload: an ordinary
    ```json or ```python block in a story survives, and a mangled proposal
    still does not reach the reader.

Planning: ADR 013 records the authoritative document shape; §§14-15/14A, D10,
C04 and BUILD-MILESTONES are updated to describe what exists. Debt is recorded
against M8 (scenario editor UX) and M9 (export of the audit trail).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PWU4gTfLYY6Qq9U7aa9Qw2

backend/tests/test_turn_flow_integration.py

@@ -18,7 +18,7 @@ from app.database import Base, SessionLocal, engine, get_db
 from app.main import app
 from app.routers import adventures
 
-from fakes import GOLD_SCHEMA, ScriptedProvider, gold_replies, gold_reply
+from fakes import tally_reply, GOLD_SCHEMA, ScriptedProvider, gold_replies, gold_reply, tally_of, tally_replies
 
 
 
@@ -46,7 +46,10 @@ def client(monkeypatch):
     setup.close()
 
     # Force a real, non-demo turn that uses the fake provider.
-    ScriptedProvider.replies = [gold_reply(AI_REPLY)]
+    # Each turn states its own running total, absolutely (ADR 010). One
+    # repeated reply would set the same total every turn, which is exactly
+    # what a delta protocol could not distinguish from adding.
+    ScriptedProvider.replies = tally_replies(AI_REPLY, 20)
     monkeypatch.setattr(adventures.turns, "OpenAICompatibleProvider", ScriptedProvider)
     monkeypatch.setattr(limits, "check_row_cap", lambda *a, **k: None)
 
@@ -66,12 +69,15 @@ def client(monkeypatch):
 
 
 def _gold(adv_id) -> int:
-    """The banked total. Reading one stat rather than the whole section keeps
-    these assertions about the rollback, not about the schema's shape."""
+    """The banked total, read out of the authoritative narrative state.
+
+    M5 moved the instrument from an RPG stat to a typed narrative fact. What
+    these assertions are about is unchanged: rollback, and which position's
+    state is current.
+    """
     db = SessionLocal()
     try:
-        player = (db.get(models.Adventure, adv_id).world_state or {}).get("player", {})
-        return player.get("gold", 0)
+        return tally_of(db.get(models.Adventure, adv_id).narrative_state)
     finally:
         db.close()
 
@@ -102,11 +108,16 @@ def test_two_turns_then_undo_reverts_only_last(client):
 
 
 def test_retry_does_not_double_apply_gold(client):
+    """A retry replaces its turn rather than stacking on top of it.
+
+    The retake states the same total the turn it replaces did, so a state that
+    had stacked would read as a value no position ever established. Before the
+    fix this file was written for, the turn's effects ran twice.
+    """
     _play(client)
     assert _gold(client.adv_id) == 10
 
-    # Before the fix, this produced 20 because the turn's effects ran twice.
-    # Now it stays 10.
+    ScriptedProvider.replies = [tally_reply("Another telling.", 10)]
     r = client.post(f"/api/adventures/{client.adv_id}/retry")
     assert r.status_code == 200, r.text
     assert _gold(client.adv_id) == 10
@@ -114,6 +125,7 @@ def test_retry_does_not_double_apply_gold(client):
 
 def test_retry_then_undo_still_clean(client):
     _play(client)
+    ScriptedProvider.replies = [tally_reply("Another telling.", 10)]
     client.post(f"/api/adventures/{client.adv_id}/retry")
     assert _gold(client.adv_id) == 10
     client.post(f"/api/adventures/{client.adv_id}/undo")