Originals cache size limit with least-recently-used eviction (closes #47)

Bounds the originals cache and evicts least-recently-used. cacheOriginalsMaxBytes default 100 GiB; the effective limit adapts down via fs.statfs to keep freeBelowBytes (default 50 GiB) free. Over-limit writes evict unpinned originals oldest-mtime-first (mtime touched on read); pinned files (favorites + latest week) are skipped and an over-budget on-demand fetch proceeds over-limit. Every in-flight write is excluded from eviction, so concurrent fetches never delete each other's just-stored file. Only cacheDirectory/originals is evicted; downloadDirectory and thumbnails never.

Model: opus-4-8

src/library/index.ts

@@ -132,6 +132,14 @@ export interface LibraryOptions {
     // Overrides the client's own `contentSource()`; mainly for tests that drive
     // the cache with a stand-in source.
     contentSource?: ContentSource;
+    // Bound on `cacheDirectory/originals` (default 100 GiB) and the free space
+    // to protect on its volume (default 50 GiB). The effective limit adapts
+    // down as the disk fills; `status().originalsLimitBytes` reports it.
+    cacheOriginalsMaxBytes?: number;
+    freeBelowBytes?: number;
+    // Whether an original is pinned and so never evicted (favorites + latest
+    // week; the precache unit #48 supplies the set).
+    isOriginalPinned?: (fileID: number) => boolean;
 }
 
 export interface LibraryStatus {
@@ -153,6 +161,10 @@ export interface LibraryStatus {
     // when ML fetching is disabled.
     mlStored?: number;
     mlIndexed?: number;
+    // Bytes stored in the originals cache and the effective size limit as of the
+    // last write or open; undefined when no content cache is open.
+    originalsUsedBytes?: number;
+    originalsLimitBytes?: number;
     closed: boolean;
 }
 
@@ -289,6 +301,9 @@ export class Library {
                 cacheDirectory,
                 downloadDirectory: opts.downloadDirectory,
                 getFile: (fileID) => store.getFileByID(fileID),
+                cacheOriginalsMaxBytes: opts.cacheOriginalsMaxBytes,
+                freeBelowBytes: opts.freeBelowBytes,
+                isPinned: opts.isOriginalPinned,
             });
             await cache.open();
         }
@@ -364,6 +379,7 @@ export class Library {
             files += this.store.listFiles(c.id).length;
         }
         const ml = this.mldata?.stats();
+        const originals = this.cache?.originalsStatus();
         return {
             userID: this.store.userID,
             collections: collections.length,
@@ -374,6 +390,8 @@ export class Library {
             lastMLError: this.lastMLError,
             mlStored: ml?.stored,
             mlIndexed: ml?.indexed,
+            originalsUsedBytes: originals?.usedBytes,
+            originalsLimitBytes: originals?.limitBytes,
             closed: this.closed,
         };
     }