feat(image): complete reviewed generation delivery

mindspace-thumbnails.mjs

@@ -1,3 +1,4 @@
+import crypto from 'node:crypto';
 import fs from 'node:fs/promises';
 import path from 'node:path';
 import { workspaceThumbnailRelativePath } from './mindspace-workspace-thumbnails.mjs';
@@ -329,6 +330,7 @@ function themeBackgroundLayers(signals) {
 
 export function buildFeedThumbnailSvg(signals, options = {}) {
   const coverDataUri = options.coverDataUri ?? null;
+  const sourceHash = String(options.sourceHash ?? '').trim();
   const hasPhoto = Boolean(coverDataUri);
   const useScenic = !hasPhoto && shouldUseScenicBackground(signals);
   const palette = resolvePhotoPalette(signals);
@@ -371,7 +373,7 @@ export function buildFeedThumbnailSvg(signals, options = {}) {
   const grainOpacity = hasPhoto ? '0.18' : '0.28';
 
   return `<?xml version="1.0" encoding="UTF-8"?>
-<svg xmlns="http://www.w3.org/2000/svg" width="${FEED_WIDTH}" height="${FEED_HEIGHT}" viewBox="0 0 ${FEED_WIDTH} ${FEED_HEIGHT}">
+<svg xmlns="http://www.w3.org/2000/svg" width="${FEED_WIDTH}" height="${FEED_HEIGHT}" viewBox="0 0 ${FEED_WIDTH} ${FEED_HEIGHT}"${sourceHash ? ` data-source-hash="${escapeXml(sourceHash)}"` : ''}>
   <defs>
     <linearGradient id="theme" x1="18%" y1="0%" x2="82%" y2="100%">
       <stop offset="0%" stop-color="${escapeXml(lighten(signals.accent, 0.12))}"/>
@@ -474,14 +476,22 @@ export async function generateHtmlThumbnail(storageRoot, storageKey, html, meta
     imageUrl: signals.image,
     resolveAssetDataUri: meta.resolveAssetDataUri,
   });
-  const svg = buildFeedThumbnailSvg(signals, { coverDataUri });
+  const sourceHash = crypto.createHash('sha256').update(String(html)).digest('hex');
+  const svg = buildFeedThumbnailSvg(signals, { coverDataUri, sourceHash });
   await writeThumbnail(storageRoot, storageKey, svg);
   return svg;
 }
 
 export async function ensureHtmlThumbnail(storageRoot, storageKey, html, meta = {}) {
   const existing = await readThumbnailIfExists(storageRoot, storageKey);
-  if (existing && isModernFeedThumbnail(existing) && !meta.force) {
+  const sourceHash = crypto.createHash('sha256').update(String(html)).digest('hex');
+  const existingSourceHash = existing?.match(/\bdata-source-hash=["']([a-f0-9]{64})["']/i)?.[1] ?? null;
+  if (
+    existing &&
+    isModernFeedThumbnail(existing) &&
+    existingSourceHash === sourceHash &&
+    !meta.force
+  ) {
     return existing;
   }
   return generateHtmlThumbnail(storageRoot, storageKey, html, meta);