docs: record the audio clock, and that CI is green

The e2e job passes on both engines for the first time, so the three
files that describe it as red are wrong. Also records the two things
that made it findable: the CI container is reproducible under Docker,
and the app's own audio stack had to be the thing measured.

.pi/skills/yellowjacket-dev/SKILL.md

@@ -56,11 +56,12 @@ reference, because you need them *before* the failure, not after.
   `--browser=webkit` is CI-only; local work is Chromium. CI runs it
   with `if: !cancelled()` so a chromium failure does not silently
   skip it, which it did for two sessions.
-- **CI's `e2e` job is red for a reason that is not yours.** Three
-  playback specs fail in the container on both engines (48 pass on
-  each) because the position never advances there — an audio-device
-  problem, not a renderer or app one. Read the per-step status before
-  assuming your change did it.
+- **CI's `e2e` job is green on both engines** (54 specs each) since the
+  container got an audio device that keeps time. If playback specs
+  start failing there again, check the **`The sink plays at real time`**
+  step first: ALSA's `null` plugin consumes 3000 ms of audio in 2.96 ms,
+  so every track finishes instantly and the clock never moves — which
+  reads as an app bug and cost two sessions of that suspicion.
 - **`make e2e` needs `SEED=default`.** Its specs assert on fixture
   content — unicode tracks, the fixture artists, a known playable file.
   Run against the `bulk` seed a measurement session left behind and 13