Precache all thumbnails and pinned originals inside open() (closes #48)

Precaches aggressively inside open(): every thumbnail (newest first, through the shared thumbnail pool, never evicted; visible/ahead requests preempt the background fill) and the pinned originals — the favorites album plus every file within precacheOriginalsDays (default 7) of the newest takenAt — through the content pool. The pinned set integrates with the #47 eviction hook; when the window moves or a favorite is removed, files become ordinary evictable originals. open() options precacheThumbnails/precacheOriginals/precacheOriginalsDays; progress via onProgress/status().

Model: opus-4-8

src/library/content.ts

@@ -328,12 +328,45 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
     }
 
     async ensureThumbnails(args: EnsureOptions): Promise<EnsureResult[]> {
-        const priority = poolPriorityOf(args.priority);
+        return this.ensureMany(
+            "thumbnail",
+            poolPriorityOf(args.priority),
+            args.fileIDs,
+            args.signal,
+            args.onProgress,
+        );
+    }
+
+    // Fill originals through the content pool for the precache (#48), always at
+    // background priority so an on-demand `original()` preempts the fill. A
+    // present original is a map lookup and no fetch; a per-file failure is
+    // returned, not thrown, so one bad file never halts a background sweep.
+    async ensureOriginals(args: {
+        fileIDs: number[];
+        signal?: AbortSignal;
+        onProgress?: (event: EnsureEvent) => void;
+    }): Promise<EnsureResult[]> {
+        return this.ensureMany(
+            "original",
+            "background",
+            args.fileIDs,
+            args.signal,
+            args.onProgress,
+        );
+    }
+
+    private async ensureMany(
+        kind: Kind,
+        priority: Priority,
+        fileIDs: number[],
+        signal: AbortSignal | undefined,
+        onProgress: ((event: EnsureEvent) => void) | undefined,
+    ): Promise<EnsureResult[]> {
         // Dedup the request list so a repeated fileID is fetched once and
         // reported once, in first-requested order.
         const seen = new Set<number>();
         const unique: number[] = [];
-        for (const id of args.fileIDs) {
+        for (const id of fileIDs) {
             if (!seen.has(id)) {
                 seen.add(id);
                 unique.push(id);
@@ -341,24 +374,20 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
         }
         return Promise.all(
             unique.map((fileID) =>
-                this.ensureOne(fileID, priority, args.signal, args.onProgress),
+                this.ensureOne(fileID, kind, priority, signal, onProgress),
             ),
         );
     }
 
     private async ensureOne(
         fileID: number,
+        kind: Kind,
         priority: Priority,
         signal: AbortSignal | undefined,
         onProgress: ((event: EnsureEvent) => void) | undefined,
     ): Promise<EnsureResult> {
         try {
-            const result = await this.acquire(
-                fileID,
-                "thumbnail",
-                priority,
-                signal,
-            );
+            const result = await this.acquire(fileID, kind, priority, signal);
             const status = result.cached ? "skipped" : "done";
             onProgress?.({ fileID, status, path: result.path });
             return { fileID, path: result.path };