docs(skill): the WAV fixtures scan tagged, and have since #104

`fixtures.md` told an agent the WAV fixtures scan in untitled, that
there is no "Field Recordings" artist in the Artists view, and that
this is a known open bug "pinned by TestWAVTagsAreNotReadableYet" — a
test #104 deleted, because it existed to assert the reader did not work
and failed the moment it did.

That last clause is why this is worth a diff rather than being left to
rot: the paragraph is an instruction, and it instructs the next reader
that a spec asserting the *working* behaviour is the mistake. It is the
same #104 staleness #217 removed from `queue-selection.spec.ts`, one
file over, still telling agents to put it back.

Measured against a running app rather than corrected from the issue
text — and the seed had to be rebuilt first, since the one on disk
predated #104 and would have replayed a pre-#104 scan and confirmed the
stale paragraph. On a fresh `make sandbox-seed NAME=default`, both WAVs
carry a title, an artist credit and an album: "Field Recordings" is an
ordinary artist with 2 tracks and "Test Tones" has a cover row. The
only two tracks with no album at all are `unsorted/no-tags-at-all.mp3`
and `unsorted/title-only.mp3`.

The replacement also says that prose written before #104 disagrees,
because it does, and saying nothing is how the next reader reintroduces
the claim from a source this change deliberately does not touch.

Deliberately carries no `Closes` footer. #225 covers two halves, and
the second — the same staleness in two *dated* `.planning/NOTES.md`
entries — is left alone: whether measured history gets a correcting
clause is a judgement about what that file is for, which the issue
raises on purpose and this change must not settle by auto-closing it.

.pi/skills/yellowjacket-dev/references/fixtures.md

@@ -42,11 +42,16 @@ strings and identical specs produce different bytes on different builds.
   playback and then clicks pause races the track ending and fails
   against a correct UI. Use `LONG_TRACK` (90 s, `edge-lengths`) exported
   from `e2e/support/fixtures.ts`.
-- **WAV tracks scan in untitled.** `backend/tagwriter` writes WAV tags
-  into a RIFF `id3 ` chunk and `dhowden/tag` has no RIFF parser, so
-  there is no "Field Recordings" artist in the Artists view. This is a
-  known open bug pinned by `TestWAVTagsAreNotReadableYet`; do not
-  "fix" a spec by asserting the broken behaviour elsewhere.
+- **WAV tracks scan like every other format.** #104 added
+  `backend/riff`, so the scan reads the `id3 ` chunk `backend/tagwriter`
+  writes and both WAVs come in fully tagged: "Field Recordings" is an
+  ordinary artist in the Artists view, with a "Test Tones" album and a
+  cover. They are therefore not an example of an untitled or albumless
+  track — the only two tracks with no album are
+  `unsorted/no-tags-at-all.mp3` and `unsorted/title-only.mp3`. Prose
+  written before #104 says the opposite and names
+  `TestWAVTagsAreNotReadableYet`, a test that change deleted; that is
+  dated history rather than a description of the app.
 
 ## Seeds