feat: copy a file's or folder's #/name@owner link from Files, Music, Photos and Search

"Copy link" puts the address group-link.js resolves on the clipboard, on the
hub's origin rather than the page's, so a link copied in the desktop
application is not app://meshbay. Files offers it for one row, from the
right-click menu or the toolbar with one row ticked (a phone's way in);
Music on one track's menu, whose dots a phone has; Photos on a right-clicked
tile and in the lightbox's bar. The video player and the file preview carry
a link button next to Download.

Applications get a `linkFor(entry | folderPath)` prop (MESHBAY_DESIGN.md
§9.2) and offer the action only when it names a link. The group page builds
it from the hub's row; Search from each result's own group and its path
before the merged views prefixed it, and names no link for a folder of the
merged tree, which a group name alone does not identify.

harness/copy_link_probe.py mounts the three applications in Chrome and reads
what reached the clipboard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
index f2c4374..9adb1e1 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
@@ -11,6 +11,7 @@ import { Menu, MenuDots, useMenu } from './menu.js';
 import { PlaylistMenuButton, NameModal, usePlaylists } from './playlist-menu.js';
 import * as P from './playlists.js';
 import { CastButton } from './cast-session.js';
+import { copyLink } from './copy-link.js';
 
 // -- Music --------------------------------------------------------------------
 //
@@ -564,7 +565,7 @@ function FlatList({ items, onPlayQueue, onMenu }) {
 function MusicApp({
   groupId, transportRef, gekRef, status, entries, availableEntries,
   musicDirectories, musicbrainzConfig, onPlayQueue, userId,
-  hideFilter, userPrefs, pageResetKey,
+  hideFilter, userPrefs, pageResetKey, linkFor,
 }) {
   const [mode, setMode] = useState(loadViewMode);
   const [filter, setFilter] = useState('');
@@ -618,6 +619,9 @@ function MusicApp({
   // argument slot for one.
   const onMenu = useCallback((e, tracks, startIndex) => {
     if (!tracks || !tracks.length) return;
+    // One track's menu — a row's, whose dots are how a phone opens it. An
+    // album's carries all its tracks and gets no link: Files has the folder's.
+    const link = tracks.length === 1 && linkFor ? linkFor(tracks[0]) : null;
     openAt(e, [
       { label: t('music.menu_play'), icon: 'play',
         onSelect: () => onPlayQueue(tracks, startIndex || 0) },
@@ -650,8 +654,10 @@ function MusicApp({
           },
         ],
       },
+      ...(link ? [{ divider: true },
+        { label: t('link.copy'), icon: 'link', onSelect: () => copyLink(link) }] : []),
     ]);
-  }, [openAt, onPlayQueue, playlists, addToPlaylist]);
+  }, [openAt, onPlayQueue, playlists, addToPlaylist, linkFor]);
 
   useEffect(() => { setMode(loadViewMode()); }, [groupId]);
   useEffect(() => { setFilter(''); }, [groupId]);