Files previews: the cache is one database file, <data dir>/thumbs.db

bbolt instead of a tree of hash-named JPEGs: pure Go, so the binary stays static; one
file per machine; an entry carries where the preview came from (engine, codec, size,
when) beside the picture, and a count rides along so the tab can say what it holds
without walking anything. A miss never creates the file, so a machine nobody browses
with previews on never has one; a cache that cannot be opened is logged and previews
are still made and served, just not kept.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

web/src/Files.tsx

@@ -192,7 +192,7 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
   const [thumbs, setThumbs] = useState<ThumbStatus | null>(null)
   const [listEl, setListEl] = useState<HTMLDivElement | null>(null)
   const near = useMemo(() => (listEl && previews ? new Near(listEl) : null), [listEl, previews])
-  const readThumbs = useCallback((refresh = false) => { api.thumbStatus(sudo, refresh).then(setThumbs).catch((e) => setThumbs({ ok: false, engine: '', summary: '', gpus: [], error: e instanceof Error ? e.message : 'failed', user: '', cache_dir: '' })) }, [sudo])
+  const readThumbs = useCallback((refresh = false) => { api.thumbStatus(sudo, refresh).then(setThumbs).catch((e) => setThumbs({ ok: false, engine: '', summary: '', gpus: [], error: e instanceof Error ? e.message : 'failed', user: '', cache: { path: '', entries: 0, bytes: 0 } })) }, [sudo])
   useEffect(() => { try { localStorage.setItem(PREVIEWS_KEY, previews ? '1' : '0') } catch { /* private mode */ } }, [previews])
   useEffect(() => { if (previews) readThumbs(); else setThumbs(null) }, [previews, readThumbs])
 
@@ -279,7 +279,7 @@ export default function Files({ onOpenInTerminal }: { onOpenInTerminal?: (cmd: s
         <div className="files-tools">
           <button className={'btn' + (sudo ? ' on' : '')} title="browse as root" onClick={() => setSudo(!sudo)}>{sudo ? 'root' : 'sudo'}</button>
           <button className={'btn' + (hidden ? ' on' : '')} title="show hidden files" onClick={() => setHidden(!hidden)}>.hidden</button>
-          <button className={'btn' + (previews ? ' on' : '')} title={'thumbnails for images and videos' + (thumbs ? ` — ${thumbs.summary}` : '')} onClick={() => setPreviews(!previews)}>previews</button>
+          <button className={'btn' + (previews ? ' on' : '')} title={'thumbnails for images and videos' + (thumbs ? ` — ${thumbs.summary}` + (thumbs.cache.entries ? ` · ${thumbs.cache.entries} kept (${fmtBytes(thumbs.cache.bytes)})` : '') : '')} onClick={() => setPreviews(!previews)}>previews</button>
           <select className="btn" value={sort} onChange={(e) => setSort(e.target.value as Sort)}><option value="name">name</option><option value="size">size</option><option value="mtime">modified</option></select>
           <input className="filter" placeholder="filter" value={q} onChange={(e) => setQ(e.target.value)} />
           <button className="btn" onClick={mkdir}>+ folder</button>

web/src/api.ts

@@ -252,7 +252,7 @@ export interface ARCView { detail: ARCDetail; live: ARCLive | null }
 export interface FileEntry { name: string; type: 'dir' | 'file' | 'link' | 'other'; size: number; mode: string; perm: string; mtime: number; user: string; group: string; target?: string; broken?: boolean; preview?: 'image' | 'video' }
 export interface ThumbGPU { api: string; device: string; name?: string; codecs?: string[]; reason?: string; permission?: boolean }
 // How previews get made on the machine: ok with an engine, or why not and what would fix it.
-export interface ThumbStatus { ok: boolean; engine: 'gpu' | 'cpu' | ''; summary: string; ffmpeg?: string; gpus: ThumbGPU[]; unusable?: ThumbGPU[]; error?: string; install?: { pm: string; package: string }; gpu_fix?: boolean; user: string; cache_dir: string }
+export interface ThumbStatus { ok: boolean; engine: 'gpu' | 'cpu' | ''; summary: string; ffmpeg?: string; gpus: ThumbGPU[]; unusable?: ThumbGPU[]; error?: string; install?: { pm: string; package: string }; gpu_fix?: boolean; user: string; cache: { path: string; entries: number; bytes: number } }
 export interface FileInfo extends FileEntry { path: string; text: boolean }
 
 const q = (path: string, sudo: boolean, extra = '') => `path=${encodeURIComponent(path)}${sudo ? '&sudo=1' : ''}${extra}`