In-process read surface: albums, photos, and timeline grouping (closes #44)

Adds the in-process read surface, served from RAM with args-object signatures: albums (list/byName/byID), photos (byID/records -> plain PhotoRecord[]), thin Album/Photo wrappers, and timeline.groups (day/week/month) with a PhotoFilter (albumID/text/fileTypes/hasLocation/includeArchived; hidden excluded). Week keys use ISO YYYY-Www; each file appears once per group, newest first. Built on the #43 snapshot projection; no network.

Model: opus-4-8

src/index.ts

@@ -36,11 +36,19 @@ export {
 export {
     Library,
     DEFAULT_REFRESH_INTERVAL_SECONDS,
+    Album,
+    Photo,
     type LibraryClient,
     type LibraryOptions,
     type LibraryStatus,
     type RefreshEvent,
     type RefreshProgressCallback,
+    type AlbumsAPI,
+    type PhotosAPI,
+    type TimelineAPI,
+    type PhotoFilter,
+    type TimelineGroup,
+    type GroupBy,
 } from "./library/index.js";
 export type {
     AlbumRecord,