feat(hub-client): attributionEnabled preference + Authorship toggle + identity threading

Closes the Phase 5c port. Restores the bits dropped from the rebase
that wire the renderer-side colouring (commit a0416b23) into the
user-facing toggle and the Automerge identity table:

- services/preferences/schema.ts: attributionEnabled boolean with
  z.default(false) so existing localStorage entries forward-compat
  without resetting other preferences.
- components/tabs/SettingsTab.tsx: "Authorship" checkbox under
  Settings → Preview.
- components/render/ReactPreview.tsx: read the preference via
  usePreference, drive useAttribution({ enabled }); accept an
  optional `identities` prop and pass it as the identities table
  so profile-metadata names win over the fnv1a fallback when
  available.
- components/render/PreviewRouter.tsx: pass-through for the new
  prop (Preview doesn't take it).
- components/Editor.tsx: thread the existing `identities`
  Automerge-presence map down to PreviewRouter.
- hooks/usePreference.test.tsx: re-target the cross-instance
  reactivity test at attributionEnabled (its original Phase 5c
  fixture), undoing the temporary errorOverlayCollapsed
  decoupling done while the preference was absent.

Off path stays byte-identical: when the toggle is off,
useAttribution short-circuits to a null payload and the WASM call
falls through to the unflagged q2-debug path.

Author: shikokuchuo

hub-client/src/components/Editor.tsx

@@ -1052,6 +1052,7 @@ export default function Editor({ project, files, fileContents, onDisconnect, onC
             onSlideChange={handleSlideChange}
             onFormatChange={handleFormatChange}
             onContentRewrite={handleContentRewrite}
+            identities={identities}
           />
         </div>
       </main>

hub-client/src/components/render/PreviewRouter.tsx

@@ -3,6 +3,7 @@ import type * as Monaco from 'monaco-editor';
 import type { FileEntry } from '../../types/project';
 import { isQmdFile } from '../../types/project';
 import type { Diagnostic } from '../../types/diagnostic';
+import type { ActorIdentity } from '../../services/automergeSync';
 import { parseQmdToAst, isWasmReady, initWasm } from '../../services/wasmRenderer';
 import Preview from './Preview';
 import ReactPreview from './ReactPreview';
@@ -29,6 +30,13 @@ interface PreviewRouterProps {
   onSlideChange?: (slideIndex: number) => void;
   onFormatChange?: (format: string | null) => void;
   onContentRewrite: (content: string) => void;
+  /**
+   * Automerge actor → display identity (name + colour). Threaded
+   * through to ReactPreview's `useAttribution` so the Authorship
+   * overlay uses profile-metadata names where available, instead
+   * of the `actor.slice(0, 8)` fallback hash.
+   */
+  identities?: Record<string, ActorIdentity>;
 }
 
 /**
@@ -113,8 +121,9 @@ export default function PreviewRouter(props: PreviewRouterProps) {
     return <NonQmdPlaceholderView filename={props.currentFile?.path ?? 'no currentFile path'} />;
   }
 
-  // Render the appropriate preview component with shared WASM error banner
-  const { onRegisterScrollToLine, onRegisterSetScrollRatio, onFormatChange, onContentRewrite, fileContents, ...commonProps } = props;
+  // Render the appropriate preview component with shared WASM error banner.
+  // `identities` is for ReactPreview only — Preview doesn't know about it.
+  const { onRegisterScrollToLine, onRegisterSetScrollRatio, onFormatChange, onContentRewrite, fileContents, identities, ...commonProps } = props;
 
   return (
     <div style={{ height: '100%', display: 'flex', flexDirection: 'column' }}>
@@ -124,7 +133,7 @@ export default function PreviewRouter(props: PreviewRouterProps) {
       )}
       <div style={{ flex: 1, overflow: 'hidden' }}>
         {reactFormat ? (
-          <ReactPreview {...commonProps} onContentRewrite={onContentRewrite} fileContents={fileContents} format={reactFormat} />
+          <ReactPreview {...commonProps} onContentRewrite={onContentRewrite} fileContents={fileContents} format={reactFormat} identities={identities} />
         ) : (
           // Phase 9 Decision 6: pass `fileContents` so any sibling
           // edit (including `_quarto.yml`) triggers a re-render via

hub-client/src/components/render/ReactPreview.tsx

@@ -2,6 +2,7 @@ import { useState, useCallback, useRef, useEffect } from 'react';
 import type * as Monaco from 'monaco-editor';
 import type { FileEntry } from '../../types/project';
 import type { Diagnostic } from '../../types/diagnostic';
+import type { ActorIdentity } from '../../services/automergeSync';
 import {
   parseQmdToAstWithAttribution,
   renderPageInProject,
@@ -10,6 +11,7 @@ import {
 } from '../../services/wasmRenderer';
 import { pipelineKindForFormat } from '../../utils/pipelineKind';
 import { useAttribution } from '../../hooks/useAttribution';
+import { usePreference } from '../../hooks/usePreference';
 import { stripAnsi } from '../../utils/stripAnsi';
 import { PreviewErrorOverlay } from './PreviewErrorOverlay';
 import ReactRenderer from './ReactRenderer';
@@ -44,6 +46,14 @@ interface PreviewProps {
   onSlideChange?: (slideIndex: number) => void;
   onContentRewrite: (content: string) => void;
   format: string; // 'q2-slides', 'q2-debug', or 'q2-preview'
+  /**
+   * Automerge actor → display identity (name + colour). Consumed
+   * by `useAttribution` to fill the `identities` half of the
+   * attribution payload. Falls back to `actor.slice(0, 8)` +
+   * `fnv1aHex8`-derived colour for any actor without a profile
+   * entry, so the Phase 6 producer invariant always holds.
+   */
+  identities?: Record<string, ActorIdentity>;
 }
 
 // Result of rendering QMD content to AST
@@ -205,6 +215,7 @@ export default function ReactPreview({
   onSlideChange,
   onContentRewrite,
   format,
+  identities,
 }: PreviewProps) {
   // Preview state machine for error handling
   const [previewState, setPreviewState] = useState<PreviewState>('START');
@@ -239,18 +250,19 @@ export default function ReactPreview({
   // payload stays `null` and the WASM call falls through to the
   // byte-identical no-attribution path.
   //
-  // The toggle UI is intentionally a separate piece of work — once a
-  // Authorship switch is plumbed through `Editor.tsx`, flipping
-  // `enabled: false` to `enabled: someToggleState` is all that's
-  // needed. Profile-metadata identity lookup (`identities`) can be
-  // wired the same way; until then the hook uses its
-  // `(actor.slice(0, 8), actorColor(fnv1aHex8(actor)))` fallback so
-  // the Phase 6 producer invariant still holds.
+  // Phase 5c — `enabled` is driven by the persisted
+  // `attributionEnabled` preference, surfaced as the "Authorship"
+  // checkbox under Settings → Preview. `identities` is the
+  // Automerge actor → display-name/colour table threaded down from
+  // `Editor.tsx`; missing entries fall back to the hook's
+  // `(actor.slice(0, 8), actorColor(fnv1aHex8(actor)))` so the
+  // Phase 6 producer invariant always holds.
+  const [attributionEnabled] = usePreference('attributionEnabled');
   const attributionPayload = useAttribution({
-    enabled: false,
+    enabled: attributionEnabled,
     filePath: currentFile?.path ?? null,
     sourceText: content,
-    identities: {},
+    identities: identities ?? {},
   });
 
   // Debounce rendering

hub-client/src/components/tabs/SettingsTab.tsx

@@ -22,6 +22,7 @@ export default function SettingsTab({
   onScrollSyncChange,
 }: SettingsTabProps) {
   const [errorOverlayCollapsed, setErrorOverlayCollapsed] = usePreference('errorOverlayCollapsed');
+  const [attributionEnabled, setAttributionEnabled] = usePreference('attributionEnabled');
   const [isCapturing, setIsCapturing] = useState(false);
 
   const handleScreenshot = async () => {
@@ -93,6 +94,18 @@ export default function SettingsTab({
             Show errors as a small indicator instead of expanded panel
           </span>
         </label>
+        <label className="setting-toggle">
+          <input
+            type="checkbox"
+            checked={attributionEnabled}
+            onChange={(e) => setAttributionEnabled(e.target.checked)}
+          />
+          <span className="setting-name">Authorship</span>
+          <span className="setting-description">
+            Colour each node by its last-touch Automerge author in the
+            debug preview
+          </span>
+        </label>
         <div style={{ marginTop: '16px' }}>
           <button
             className="screenshot-button"