feat: add tags/labels for saved items

- Add free-form tags per item: chip display with remove, inline add (comma-separated, grid view only), and a toolbar tag-filter popover listing every tag in use
- Search now also matches tags; tags sync across devices like every other item field
- Fix Firefox manifest.json compliance for AMO submission: replace the placeholder gecko id with a real UUID, add the now-required data_collection_permissions (bookmarksInfo, since synced items are personal browsing/bookmark data), and bump strict_min_version to 140.0 (142.0 for gecko_android) to match
- Add description.md (elevator pitch / short / detailed descriptions for store listings), PRIVACY.md, and .gitignore for the dist/ packaging output
- Reword all em-dash punctuation across docs and code comments per user preference

sync.js

@@ -3,7 +3,7 @@
 // and newtab.html (via <script>, Firefox event page + the shelf UI).
 //
 // Sync storage only ever holds a lightweight metadata projection of each
-// item (no screenshot thumbnails — chrome.storage.sync caps a single key at
+// item (no screenshot thumbnails; chrome.storage.sync caps a single key at
 // 8KB), one key per item ("m_<id>") so the per-key cap is never a problem;
 // the 512-key / ~100KB total quota is the real ceiling. All sync writes are
 // best-effort: if the user isn't signed in, is offline, or is over quota,
@@ -13,6 +13,7 @@
 const SYNC_KEY_PREFIX = "m_";
 const SYNCED_IDS_KEY = "shelfSyncedIds";
 const FAVICON_SYNC_MAX_LEN = 1000;
+const TAGS_SYNC_MAX_COUNT = 20;
 
 function syncKeyFor(id) {
   return SYNC_KEY_PREFIX + id;
@@ -20,7 +21,7 @@ function syncKeyFor(id) {
 
 // Shared by the reminder highlight and the auto-delete sweep, in both
 // background.js and newtab.js, so the two periods can never drift apart.
-// Months are approximated as 30 days — no need for calendar precision here.
+// Months are approximated as 30 days; no need for calendar precision here.
 const UNIT_MS = { days: 86400000, weeks: 604800000, months: 2592000000 };
 
 function periodMs(amount, unit) {
@@ -32,7 +33,7 @@ function periodMs(amount, unit) {
 // invariant as the settings-panel validation, as a hard safety net: even if
 // prefs somehow end up misconfigured (e.g. edited directly in storage), this
 // refuses to delete anything until the auto-delete period genuinely exceeds
-// the reminder period — so a user is always reminded before something is
+// the reminder period, so a user is always reminded before something is
 // removed, never surprised by it.
 function isOverdueForDeletion(item, prefs) {
   if (!prefs || !prefs.autoDeleteEnabled || item.archived) return false;
@@ -54,16 +55,17 @@ function metaFromItem(item) {
     updatedAt: item.updatedAt || item.dateAdded,
     surfaceCount: item.surfaceCount || 0,
     lastSurfacedAt: item.lastSurfacedAt || 0,
+    tags: (item.tags || []).slice(0, TAGS_SYNC_MAX_COUNT),
   };
 }
 
 // "Worth a second look" spotlight: proactively resurfaces a few old,
 // forgotten, unarchived items on the new tab page. The more times an item
 // has been surfaced without being acted on, the longer before it's shown
-// again — so it never nags forever on the same links, but never fully goes
+// again, so it never nags forever on the same links, but never fully goes
 // silent either (it always comes back eventually).
 const SPOTLIGHT_BACKOFF_DAYS = [3, 7, 14, 30, 60];
-// Used when the reminder feature is off (its default state) — otherwise
+// Used when the reminder feature is off (its default state). Otherwise
 // "old enough to matter" would have no threshold at all and the spotlight
 // would silently do nothing for most users.
 const SPOTLIGHT_FALLBACK_MIN_AGE_MS = periodMs(14, "days");
@@ -122,7 +124,7 @@ async function writeSyncedIds(idSet) {
 
 // Pulls remote adds/edits into `items` and pushes local adds/edits/deletes
 // out to chrome.storage.sync. Returns the merged items array; does not
-// persist it — callers are responsible for saving the result locally.
+// persist it. Callers are responsible for saving the result locally.
 async function reconcileWithSync(items) {
   let syncItems, previouslySynced;
   try {
@@ -135,7 +137,7 @@ async function reconcileWithSync(items) {
   const localById = new Map(items.map((i) => [i.id, i]));
 
   // Items that were synced before but are no longer in sync storage were
-  // deleted on another device — drop them here too.
+  // deleted on another device, so drop them here too.
   let merged = items.filter((item) => !(previouslySynced.has(item.id) && !syncById.has(item.id)));
 
   // Pull in remote adds/edits.
@@ -143,8 +145,8 @@ async function reconcileWithSync(items) {
     const local = localById.get(meta.id);
     if (!local) {
       // Absent locally but previously synced means *this* device deleted it;
-      // don't resurrect it from a remote copy that hasn't caught up yet —
-      // let the deletion below propagate out instead.
+      // don't resurrect it from a remote copy that hasn't caught up yet.
+      // Let the deletion below propagate out instead.
       if (previouslySynced.has(meta.id)) continue;
       merged.push({
         id: meta.id,
@@ -158,6 +160,7 @@ async function reconcileWithSync(items) {
         updatedAt: meta.updatedAt,
         surfaceCount: meta.surfaceCount || 0,
         lastSurfacedAt: meta.lastSurfacedAt || 0,
+        tags: meta.tags || [],
       });
     } else if ((meta.updatedAt || 0) > (local.updatedAt || local.dateAdded || 0)) {
       local.title = meta.title;
@@ -168,6 +171,7 @@ async function reconcileWithSync(items) {
       local.updatedAt = meta.updatedAt;
       local.surfaceCount = meta.surfaceCount || 0;
       local.lastSurfacedAt = meta.lastSurfacedAt || 0;
+      local.tags = meta.tags || [];
     }
   }
 
@@ -198,7 +202,7 @@ async function reconcileWithSync(items) {
     if (removals.length) await chrome.storage.sync.remove(removals);
     await writeSyncedIds(nextSyncedIds);
   } catch {
-    // Best effort — local storage remains the source of truth for this device.
+    // Best effort: local storage remains the source of truth for this device.
   }
 
   return merged;