Files pane and item buttons are icons, with the words in tooltips

Save, delete, view and download in the Files pane, and mark read, keep
and open the original under an item's title, are icons now. The word is
in each one's title and aria-label, so it is still there on hover and
for screen readers. Tests find them by title or action, not text.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016HdTEWQNrzyFULijigkmMn

CHANGELOG.md

@@ -28,6 +28,8 @@ The long form, with what was wrong before and how it was found, is in
   items show without pressing Scan.
 - A file deleted to save space, or by hand, looks as if it was never downloaded: no "reaped"
   label, just the Download button. The retention summary says "deleted", not "reaped".
+- The Files pane and an item's own buttons are icons, with the words in their tooltips: save,
+  delete, view, download, mark read, keep, and open the original.
 
 ### Security