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 A fact withdrawn by a manual correction is now named as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

@@ -5,6 +5,7 @@ their own `ScriptedProvider`, and the copies had drifted into four different
 feature sets, so a test that needed to raise a provider error had to be written
 in one of the files whose copy supported it.
 """
+import json
 
 
 class ScriptedProvider:
@@ -48,35 +49,110 @@ class ScriptedProvider:
 # that a rollback failure is arithmetic rather than a judgement call: if a take
 # stacks instead of replacing, the total is off by exactly one turn's worth.
 #
-# That instrumentation used to be a JavaScript `output` hook doing
-# `state.gold += 10` in the QuickJS sandbox. M2 removed campaign scripting, and
-# the tests below are not about scripting — they are about the state snapshot,
-# rollback, and branch-isolation machinery in `attempts.py` and `tree.py`,
-# which is unchanged.
+# The instrument has moved twice, and both moves were the same move: it follows
+# whatever the production state path is, so the tests exercise real code rather
+# than a test hook. It began as a QuickJS `state.gold += 10` (removed with
+# scripting in M2), became an RPG world-state delta block (M3/M4), and is now a
+# typed narrative-state event (M5).
 #
-# The counter therefore moved to the world-state engine, which is a real
-# remaining product path: the model emits a ```state delta block, the referee
-# applies it, and the result lands in `adventure.world_state`. The fake
-# provider decides what the model "emits", so it is exactly as deterministic as
-# the script was, and it exercises production code rather than a test hook.
+# What the tests using it measure is unchanged, and worth restating because it
+# is why they were re-instrumented rather than deleted: the state at a story
+# position, rollback, Redo restoration, retry, alternate takes, divergence,
+# abandoned-future isolation, and Save Point restore. None of that was ever
+# about gold, or about RPG stats.
+#
+# The M5 instrument is deliberately genre-neutral: a `chronicle` entity — a
+# concept, not a character, not an item — carrying one named attribute. Every
+# reply sets it to an ABSOLUTE total, which is ADR 010's whole point. A delta
+# protocol could not tell "+10" from "= 10"; here the event type says which, so
+# `TALLY_PER_TURN * n` after n turns is arithmetic rather than an assumption.
 
-#: A schema with a plain unbounded counter. No `max_delta_per_turn` and no
-#: `cooldown`, so every +10 is applied in full, every turn.
-GOLD_SCHEMA = {
-    "player": {
-        "hp": {"min": 0, "max": 100, "initial": 100},
-        "gold": {"min": 0, "max": 1_000_000, "initial": 0},
-    }
-}
+#: The instrument is a fact, not an entity attribute, and deliberately so.
+#: `set_entity_attribute` names an entity that must already exist, which is the
+#: right rule for the product and the wrong one for an instrument that tests
+#: script in isolation — a one-off reply in the middle of a test would be
+#: refused for a reference the test never meant to be about. `add_fact` needs no
+#: subject, so any reply can state the tally on its own. Entity creation,
+#: possession and the referential rule get their own tests in
+#: `test_narrative_state.py`, where they are the subject rather than scaffolding.
+TALLY_PREDICATE = "tally"
+TALLY_PER_TURN = 10
 
-GOLD_PER_TURN = 10
+# Kept as an alias so the many tests that speak in these terms keep reading
+# naturally. The number is the same; only the protocol underneath changed.
+GOLD_PER_TURN = TALLY_PER_TURN
+
+#: A scenario schema is no longer needed for state to work — narrative state is
+#: not an opt-in RPG layer. The name survives for fixtures that still pass
+#: something, and empty is the honest value: this campaign has no RPG layer, and
+#: under M5 it does not need one to have state.
+GOLD_SCHEMA: dict = {}
 
 
-def gold_reply(text: str, amount: int = GOLD_PER_TURN) -> str:
-    """A model reply that narrates `text` and banks `amount` gold."""
-    return f'{text}\n```state\n{{"player.gold": {amount}}}\n```'
+def state_block(events: list) -> str:
+    """The fenced block the model is asked to emit, around `events`."""
+    return "```state\n" + json.dumps({"events": events}, ensure_ascii=False) + "\n```"
 
 
-def gold_replies(prefix: str = "Take", count: int = 40) -> list[str]:
-    """`count` numbered replies, each banking one turn's worth of gold."""
-    return [gold_reply(f"{prefix} {n}.") for n in range(1, count + 1)]
+def tally_reply(text: str, total: int) -> str:
+    """A reply that narrates `text` and records the tally as `total`.
+
+    Absolute, always — which is the whole of ADR 010. A delta protocol could not
+    tell "+10" from "= 10"; here the event says which, so `TALLY_PER_TURN * n`
+    after n turns is arithmetic rather than an assumption, and a replayed or
+    duplicated reply cannot silently double it.
+
+    Each reply supersedes the last, so the newest active tally fact is the
+    current one and the document does not grow without bound.
+    """
+    return f"{text}\n" + state_block([{
+        "type": "add_fact",
+        "predicate": TALLY_PREDICATE,
+        "value": total,
+        "fact_id": f"tally-{total}",
+    }])
+
+
+def gold_reply(text: str, amount: int = TALLY_PER_TURN) -> str:
+    """One reply banking `amount`, for tests that build a single reply.
+
+    The value is absolute underneath, so a caller asking for the default gets
+    the first turn's total, which is what those call sites mean.
+    """
+    return tally_reply(text, amount)
+
+
+def tally_replies(prefix: str = "Take", count: int = 40) -> list:
+    """`count` numbered replies whose tally runs 10, 20, 30 …"""
+    return [
+        tally_reply(f"{prefix} {n}.", n * TALLY_PER_TURN)
+        for n in range(1, count + 1)
+    ]
+
+
+#: The historical name, unchanged in meaning for every caller.
+gold_replies = tally_replies
+
+
+def tally_of(state) -> int:
+    """Reads the instrument back out of a narrative state document.
+
+    The newest active tally fact wins, which is what "absolute assignment"
+    means when the assignments are appended. Returns 0 when the campaign has
+    recorded none — what "no turns have been played" means, and what a restore
+    to before the first turn should produce.
+    """
+    if not isinstance(state, dict):
+        return 0
+    facts = state.get("facts")
+    if not isinstance(facts, list):
+        return 0
+    for fact in reversed(facts):
+        if (
+            isinstance(fact, dict)
+            and fact.get("predicate") == TALLY_PREDICATE
+            and fact.get("status", "active") == "active"
+            and isinstance(fact.get("value"), (int, float))
+        ):
+            return fact["value"]
+    return 0