feat: add Photos group app

A new group application (docs/apps.md's plug-in mechanism), following the
plan in docs/photos.md. Unlike Videos/Music: several photo roots per group
instead of one (photo_roots is a set, one signed op replaces it whole),
a single album-grid view with no third-party matching step, and per-photo
info read from the file's own EXIF at index time — no metadata service,
no credential, no outbound network call at all.

Protocol (meshbay-common, MNP 0.10 -> 0.11, additive): `taken_at`/`camera`
on IndexEntry; `photo_roots`/`photo_roots_ack`; `OP_PHOTO_ROOTS`.

Node: roster.py stores photo_roots as a group_settings entry (JSON list,
same shape as enabled_apps); ops.py/webrtc_server.py validate and sign the
whole set in one op, same pattern as apps_enabled; a new PhotoEnricher
(indexer/enrich_photo.py) runs Pillow in its own small bounded pool,
separate from the video/audio pools, producing a resized thumbnail plus
the two EXIF fields — never GPS, checked by a grep-based regression test.

Client: photos-app.js — one album card per directory containing images,
a per-album photo grid, and a lightbox with next/previous (keyboard and
buttons), zoom in/out/fit/100% starting from the actual on-screen fit
percentage, and a "zip this album" button reusing files-app.js's own zip
mechanism (lifted into file-utils.js's downloadDirectory so both call the
same implementation). group-settings.js gets an add/remove multi-root
picker, distinct from Videos/Music's single-value one.

Bugs found and fixed before this ever shipped, worth keeping the story of:

- enrich_photo.py read width/height from the raw image *before* applying
  EXIF orientation correction, and read DateTimeOriginal off the plain
  0th-IFD Exif object — a real camera stores it in the Exif sub-IFD, which
  Pillow only exposes via get_ifd(Exif). A flat, hand-built EXIF dict
  round-trips through Pillow either way, which is exactly what would have
  hidden both bugs; the regression test builds EXIF with piexif instead,
  matching what real hardware produces.
- photos-app.js's album grouping stripped a trailing path segment from
  entry.path under the assumption it still carried a filename — it
  doesn't (files-app.js's own convention: e.path is already the
  containing directory), so every album collapsed one level into its
  parent. Found live against a real multi-folder library.
- transport.js's ADMIN_OP_TYPES allowlist (already the fix for an
  identical bug on video_root/apps_enabled, see 4783d81) was missing
  photo_roots: its admin_challenge matched no pending request and was
  silently dropped, so saving a photo root just timed out after 30s with
  no error.
- daemon.py pruned a thumbnail when its file left the index (root removed
  or reconfigured) but never forgot the content hash was "already
  attempted" — the same bytes reappearing under a renamed/relocated root
  (an operator's real workflow) were then permanently skipped, forever,
  with nothing to indicate why. Discarding the attempt alongside the
  cache entry on prune is what makes pruning actually reversible.
- packages/meshbay-client's app:// protocol handler served every file
  with no Cache-Control header, so Chromium was free to serve a stale
  cached copy indefinitely — none of several `npm run sync-ui` + reload
  cycles during development actually picked up the new code until the
  renderer's disk cache was cleared by hand. Now sends Cache-Control:
  no-store.
- the lightbox's zoomed image used flex centering (align-items/
  justify-content: center) combined with overflow: auto — a well-known
  trap where the browser centers overflowing content by shifting it, and
  the leading half of that overflow (here, the top of a zoomed photo)
  sits outside what the scrollport can actually reach. Reported live as
  "unusable". Fixed by switching to top/left alignment once zoomed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TiZG4AuSnxHohQMpwTHTyL

1 files changed, 91 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js b/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
index a005e2e..b44d105 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/file-utils.js
@@ -1,5 +1,7 @@
 import * as downloads from './downloads.js';
 import * as platform from './platform.js';
+import { t } from './i18n.js';
+import { ZipStream, entriesUnder } from './zipstream.js';
 
 const FILE_ICONS = {
   video: '\u{1F3AC}', audio: '\u{1F3B5}', image: '\u{1F5BC}',
@@ -200,8 +202,97 @@ async function downloadEntry(transfers, transport, gek, entry) {
   });
 }
 
+/**
+ * Download a directory as a zip, written straight to disk.
+ *
+ * An archive of a group directory is routinely tens of gigabytes, so it is
+ * never held anywhere: each file is fetched chunk by chunk, decrypted, and
+ * handed to the zip writer, which hands it to the file the browser opened.
+ * Peak memory is one chunk plus one small record per file.
+ *
+ * Without the File System Access API there is nowhere to stream to, and the
+ * only alternative is to build the whole thing in memory — so that path is
+ * offered but says what it costs first.
+ *
+ * Lifted out of files-app.js (docs/photos.md §3) so photos-app.js's own
+ * "zip this album" button calls the same implementation rather than a
+ * second one — nothing here is Files-specific once `entries`/`transport`/
+ * `gek`/`setError` are passed in, the same shared-context shape every app
+ * already receives (apps.md §2).
+ */
+async function downloadDirectory(transfers, transport, gek, entries, dir, { setError }) {
+  if (!transport || !transport.connected) return;
+
+  const files = entriesUnder(entries, dir);
+  if (!files.length) {
+    setError(t('group.zip_empty'));
+    return;
+  }
+  const totalBytes = files.reduce((n, f) => n + (f.entry.size || 0), 0);
+  const suggested = (dir.split('/').pop() || 'files') + '.zip';
+
+  // totalBytes decides how this is delivered, but it is not the archive's
+  // size — headers and the central directory come on top — so it is not
+  // announced as a Content-Length that the download would then miss.
+  const target = await _openDownloadTarget(suggested, totalBytes, {
+    types: [{ description: 'ZIP archive',
+              accept: { 'application/zip': ['.zip'] } }],
+  }, 0);
+  if (target === false) return;
+  if (!target && !confirm(t('group.zip_no_stream', {
+    size: formatSize(totalBytes), name: suggested,
+  }))) {
+    return;
+  }
+  const zipOpenRef = { url: null };
+
+  transfers.start({
+    kind: 'download', name: (target && target.name) || suggested,
+    total: totalBytes, transport,
+    open: target
+      ? (target.open || null)
+      : () => { if (zipOpenRef.url) window.open(zipOpenRef.url, '_blank'); },
+    run: async ({ signal, onProgress }) => {
+      const writable = target ? target.writable : null;
+      const parts = writable ? null : [];
+      let written = 0;
+      try {
+        const zip = new ZipStream(async (bytes) => {
+          if (writable) await writable.write(bytes);
+          else parts.push(bytes.slice());
+        });
+
+        for (const { entry, name } of files) {
+          await zip.begin(name, entry.size,
+                          new Date((entry.added_at || 0) * 1000));
+          // A zero-byte file has no chunk to ask for; the header and an empty
+          // descriptor are the whole entry.
+          const totalChunks = Math.ceil(entry.size / CHUNK_SIZE);
+          if (totalChunks > 0) await pipelinedDownload(
+            transport, gek, entry.id, totalChunks,
+            (bytes) => { written += bytes; onProgress(written, totalBytes); },
+            // pipelinedDownload writes in order, which the archive needs.
+            { write: (plaintext) => zip.write(plaintext) }, signal);
+          await zip.end();
+        }
+        await zip.finish();
+        if (writable) await writable.close();
+        else {
+          const blob = new Blob(parts, { type: 'application/zip' });
+          _saveBlob(blob, suggested);
+          zipOpenRef.url = URL.createObjectURL(blob);
+        }
+      } catch (err) {
+        if (writable) await writable.abort().catch(() => {});
+        throw err;
+      }
+    },
+  });
+}
+
 export {
   FILE_ICONS,
   formatSize, formatDate, PREVIEWABLE_TEXT, canPreview, CHUNK_SIZE,
   _openDownloadTarget, _saveBlob, _b64ToU8, pipelinedDownload, downloadEntry,
+  downloadDirectory,
 };