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 A fact withdrawn by a manual correction is now named as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

planning/BUILD-MILESTONES.md

@@ -1,6 +1,6 @@
 # Adventure Storyteller — Production Build Milestones
 
-**Status:** In implementation. M1-M4 complete and accepted (M1 and M2: 2026-09-02; M3 and M4: 2026-09-03); M5 — Genre-Neutral Authoritative Narrative State — next to brief  
+**Status:** In implementation. M1-M5 complete and accepted (M1 and M2: 2026-09-02; M3 and M4: 2026-09-03; M5: 2026-09-04, after an independent review and a corrective pass); M6 — Branch-Safe Context, Summaries, and Long-Term Story Memory — next to brief  
 **Base:** AI-DnD `d72f7c1bda0f34fccd84afb7a25c34eb01c901de`
 
 ## 1. Purpose
@@ -591,6 +591,52 @@ treat the edited text as accepted output, re-evaluate the implied state, create
 new continuation, and retain the original. The refusal in §14A is then replaced
 by that behavior rather than kept alongside it.
 
+**Delivered in the M5 corrective pass.** The first M5 implementation did the
+state half only and kept editing the row in place, which the independent review
+found broke the head/state invariant. A narrator edit now forks — the original
+narration and its whole future are retained untouched, and the correction
+becomes a new active continuation carrying its own re-derived state. The §14A
+refusal is gone for narrator turns and remains only for a player's own input
+(§13), which M5 did not change.
+
+---
+
+## M5 — Outcome
+
+**Complete and accepted, 2026-09-04**, after an independent implementation
+review (`planning/reports/M5-IMPLEMENTATION-REPORT.md`) and the corrective pass
+recorded in that report's addendum.
+
+Delivered:
+
+- Genre-neutral typed narrative state per ADR 010, with the authoritative
+  document shape now recorded in
+  [ADR 013](DECISIONS/013-authoritative-narrative-state-document.md).
+- **D10 complete.** A narrator edit returns to the state before the turn, uses
+  the reader's exact text, re-derives the state it implies, becomes a new active
+  continuation, and retains the original narration and its future
+  (`STORY-BRANCH-SEMANTICS.md` §§14-15).
+- **Pre-M5 compatibility.** Migration 88 backfills the empty narrative document
+  onto every action written before M5, and a missing snapshot restores the empty
+  document rather than leaving a later position's state standing. Old campaigns,
+  Save Points, branches and transcripts stay usable, and no legacy RPG machinery
+  becomes authoritative again.
+- **Manual corrections govern the narrator's context.** Replayed history carries
+  prose only, and a withdrawn fact is named as no longer true rather than
+  silently dropped.
+
+Debt carried forward, deliberately:
+
+- **M8 (browser UX):** the scenario editor still exposes the legacy RPG stat
+  schema. Its copy no longer claims that schema is how the story is tracked, but
+  the screen itself is M8's to redesign.
+- **M9 (export/recovery):** `state_events` and `state_proposals` are not carried
+  in an export, so an imported campaign keeps a correction's effect but not its
+  audit trail. C04 therefore passes for a live campaign and not across a round
+  trip.
+- **§13 (editing player input)** is still an in-place edit guarded by the
+  off-screen refusal. Bringing it onto the §§14-15 footing was out of M5's scope.
+
 ---
 
 # M6 — Branch-Safe Context, Summaries, and Long-Term Story Memory