feat: cache keywords in search_progress.json — restarts reuse same keywords, no regeneration mid-run

lib/search_progress.mjs

@@ -33,6 +33,19 @@ export function initProgress(dataDir, lookbackDays) {
   return progress;
 }
 
+/** Save generated keywords for a track — reused on resume, never regenerated mid-run */
+export function saveKeywords(platform, track, keywords) {
+  if (!progress) return;
+  if (!progress.keywords) progress.keywords = {};
+  progress.keywords[`${platform}:${track}`] = keywords;
+  save();
+}
+
+/** Get saved keywords for a track, or null if not yet generated */
+export function getSavedKeywords(platform, track) {
+  return progress?.keywords?.[`${platform}:${track}`] ?? null;
+}
+
 export function isCompleted(platform, track) {
   if (!progress) return false;
   return progress.completed.includes(`${platform}:${track}`);