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 A fact withdrawn by a manual correction is now named as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

@@ -27,13 +27,13 @@ os.environ["AIDND_DB_PATH"] = db_path
 os.environ.pop("AIDND_DATABASE_URL", None)
 os.environ.pop("DATABASE_URL", None)
 
-from fakes import GOLD_PER_TURN, gold_reply  # noqa: E402
+from fakes import TALLY_PER_TURN, tally_reply  # noqa: E402
 
 _turn = itertools.count(1)
 
 
 class DeterministicProvider:
-    """Banks one turn's worth of gold per reply, numbered so text is checkable.
+    """Records a running tally per reply, numbered so the text is checkable.
 
     The same instrumentation `test_head_cursor.py` and `test_save_points.py`
     use, for the same reason: it makes "the state at this position" a number the
@@ -47,7 +47,11 @@ class DeterministicProvider:
         pass
 
     async def generate(self, parts, *, temperature, max_tokens):
-        yield ("text", gold_reply(f"Beat {next(_turn)}."))
+        n = next(_turn)
+        # An absolute running total (M5, ADR 010): turn n states n * 10, so the
+        # value a position holds is a fact about that position rather than about
+        # how many times something was added.
+        yield ("text", tally_reply(f"Beat {n}.", n * TALLY_PER_TURN))
 
 
 from app.routers.adventures import turns  # noqa: E402