Do not offer a player for a file that is not audio or video

The media-type filter stopped new image enclosures being fetched, but ones
already on disk still got a play button and an <audio> element, because
the UI tested for a path rather than for a playable type. Four places did
this, including play() itself, which picked the first downloaded enclosure
whatever it was.

isPlayable() checks audio/* or video/*, falling back to the extension when
a feed declares no type. A downloaded non-media file now shows as its kind
with Save and Delete, so it stays available without posing as an episode.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AdXho5tTkjFLeUXKbEjKBh

PROGRESS.md

@@ -56,6 +56,26 @@ and until now nothing set them.
 
 ---
 
+## 2026-09-10 — A file is not the same as a playable file
+
+Reported: "Abort Retry Fail still shows downloaded and audio playback UI". The media-type filter
+stopped *new* image enclosures being fetched, but those 20 JPEGs were already on disk from before
+it existed — and the UI gave a play button and an `<audio>` element to anything with a `path`. An
+audio element pointed at a JPEG is just a broken player.
+
+`isPlayable()` now separates having a file from being playable: audio/* or video/*, falling back to
+the file extension when a feed declares no type. Four places used the wrong test — the row's play
+button, the artwork's play overlay, `encBox`, and `play()` itself, which picked the first downloaded
+enclosure regardless of what it was. A downloaded non-media file now shows as
+`image · downloaded · Save · Delete file`, so it is still there and still retrievable, just not
+pretending to be an episode.
+
+Covered by a new browser test with a fixture blog whose entry carries a JPEG enclosure and a feed
+configured to download it: no play button on the row, no `<audio>` in the detail pane, and the Save
+button still present.
+
+---
+
 ## 2026-09-10 — Three-pane layout
 
 Ray asked for feeds beside, items above, and the selected item's text with its enclosures below —