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 A fact withdrawn by a manual correction is now named as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_change_visibility.py

@@ -207,29 +207,67 @@ def test_the_demo_asks_for_the_turn_counter():
 # What the model is told about its own refused changes
 # --------------------------------------------------------------------------- #
 
-def test_history_replays_what_was_accepted_not_what_was_sent():
-    """The contradiction that taught the model to repeat itself.
+def test_history_replays_prose_without_the_protocol_block():
+    """M5 corrective pass (review Finding 4): replayed history is prose only.
 
-    `arrows` is at its ceiling, so `+2` changes nothing. Replaying the sent
-    delta showed the model a change the live values disagreed with.
+    The block used to be reconstructed into each past AI turn so the model would
+    copy the output format. That put a second, older account of the world into
+    the same prompt as the authoritative one with nothing marking which
+    governed — and a fact the reader had explicitly withdrawn came back as an
+    accepted event, phrased as the model first asserted it. The format
+    instruction survives in `EMIT_RULE` and `EMIT_REMINDER`; the contradiction
+    does not.
     """
     from app.context.builder import _history_text
 
-    a = action({"player.arrows": 2, "player.hp": -10})
-    a.text = "The arrow flies."
+    a = models.Action(
+        type="ai",
+        text="The arrow flies.",
+        state_changes={
+            "accepted": [{"type": "add_fact", "predicate": "the arrow struck"}],
+            "rejected": [{"event": {"type": "set_possession", "item": "ghost",
+                                    "owner": "mara"},
+                          "reason": "unknown_reference", "detail": "no ghost"}],
+            "summary": ["fact: the arrow struck"],
+        },
+    )
     replayed = _history_text(a)
-    assert '"player.hp": -10' in replayed
-    assert "arrows" not in replayed
+    assert replayed == "The arrow flies."
+    assert "```state" not in replayed
+    assert "add_fact" not in replayed
+    # Neither the accepted event nor the refused one is asserted again.
+    assert "ghost" not in replayed
 
 
-def test_history_replay_keeps_flags_and_milestones_and_text():
+def test_history_replay_carries_no_machine_readable_payload():
+    """Whatever a turn accepted, the history the model reads is the story."""
     from app.context.builder import _history_text
 
-    a = action({"flags.has_key": True, "milestones.rescue_gwen": True})
-    a.text = "The lock gives."
+    a = models.Action(
+        type="ai",
+        text="The lock gives.",
+        state_changes={
+            "accepted": [
+                {"type": "open_story_thread", "thread": "the-vault",
+                 "title": "Open the vault"},
+            ],
+            "rejected": [],
+            "summary": [],
+        },
+    )
     replayed = _history_text(a)
-    assert '"flags.has_key": true' in replayed
-    assert '"milestones.rescue_gwen": true' in replayed
+    assert replayed == "The lock gives."
+    assert "open_story_thread" not in replayed
+    assert "the-vault" not in replayed
+
+
+def test_a_turn_that_changed_nothing_replays_as_prose_alone():
+    """An empty block in the replayed history reads as a turn worth reporting
+    nothing about, which is not the same as a turn that reported nothing."""
+    from app.context.builder import _history_text
+
+    a = models.Action(type="ai", text="Silence.", state_changes=None)
+    assert _history_text(a) == "Silence."
 
 
 def test_a_refusal_reaches_the_model_with_the_valid_names():