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 A fact withdrawn by a manual correction is now named as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

frontend/src/pages/Play/index.jsx

@@ -23,6 +23,7 @@ import { InsightsPanel } from './panels/InsightsPanel'
 import { MemoryPanel } from './panels/MemoryPanel'
 import { PlotPanel } from './panels/PlotPanel'
 import { SavePointPanel } from './panels/SavePointPanel'
+import { StatePanel } from './panels/StatePanel'
 
 const MODES = ['do', 'say', 'story']
 const PLAYER_TYPES = ['do', 'say', 'story']
@@ -69,7 +70,7 @@ export default function Play() {
   const [busy, setBusy] = useState(false)
   const [toast, setToast] = useState(null)
   const [editing, setEditing] = useState(null)
-  const [panel, setPanel] = useState(null) // null | 'plot' | 'memory' | 'branches' | 'savepoints' | 'insights'
+  const [panel, setPanel] = useState(null) // null | 'state' | 'plot' | 'memory' | 'branches' | 'savepoints' | 'insights'
   // Bumped when something outside the turn loop changes the drawers' state
   // (currently "Update from scenario"), which no action count would reflect.
   const [stateKey, setStateKey] = useState(0)
@@ -453,6 +454,15 @@ export default function Play() {
     }
     try {
       const updated = await api.updateAction(id, actionId, text)
+      // Correcting narrator prose the story is telling is not a rewrite of a
+      // row: STORY-BRANCH-SEMANTICS §§14-15 make it a new continuation, so the
+      // server answers with a different node and the old narration keeps its
+      // future on the line it was written on. The shape of the story changed,
+      // and only the server can say what the transcript is now.
+      if (updated.id !== actionId) {
+        await resync()
+        return
+      }
       // A take that is only being read is not in `actions` — the row there is
       // the live one — so the new text goes back into the preview, which is
       // what that row is drawing. The pager holds the take list it fetched, so
@@ -464,6 +474,10 @@ export default function Play() {
       } else {
         setActions((prev) => prev.map((a) => (a.id === actionId ? updated : a)))
       }
+      // Editing a take the story is not telling changes that take's words and
+      // nothing else, but the panel is keyed on this and would otherwise keep
+      // drawing what it last read.
+      setStateKey((k) => k + 1)
     } catch (err) {
       setToast({ text: err.message, isError: true })
     }
@@ -540,6 +554,8 @@ export default function Play() {
         <div className="page-header">
           <h1>{adventure.title}</h1>
           <div className="panel-toggles">
+            <button className={panel === 'state' ? 'active' : ''}
+              onClick={() => setPanel(panel === 'state' ? null : 'state')}>Story State</button>
             <button className={panel === 'plot' ? 'active' : ''}
               onClick={() => setPanel(panel === 'plot' ? null : 'plot')}>Plot</button>
             <button className={panel === 'memory' ? 'active' : ''}
@@ -763,12 +779,22 @@ export default function Play() {
         <div className="side-panel">
           <div className="side-panel-header">
             <h2>{{
-              plot: 'Plot Components', memory: 'Memory Bank', branches: 'Branches',
-              savepoints: 'Save Points', insights: 'Insights',
+              state: 'Story State', plot: 'Plot Components', memory: 'Memory Bank',
+              branches: 'Branches', savepoints: 'Save Points', insights: 'Insights',
             }[panel]}</h2>
             <button onClick={() => setPanel(null)}>✕</button>
           </div>
-          {panel === 'plot' ? (
+          {panel === 'state' ? (
+            // Keyed on the same signal the other live panels use, so the state
+            // follows Undo, Redo and a Save Point restore — what it shows is
+            // the state at the position being read, not at the newest turn.
+            <StatePanel
+              advId={id}
+              refreshKey={`${actions.length}:${stateKey}`}
+              onCorrected={() => setStateKey((k) => k + 1)}
+              onError={(message) => setToast({ text: message, isError: true })}
+            />
+          ) : panel === 'plot' ? (
             <PlotPanel adventure={adventure} setAdventure={setAdventure}
               onWorldStateChanged={() => setStateKey((k) => k + 1)} />
           ) : panel === 'memory' ? (