docs(player): close three of the four gaps with a real device

A Light Phone III (Android 14, SDK 34, arm64, Chrome 113 at 424x439)
was attached after the PR was opened, so what it listed as
unverifiable was checked rather than left as a caveat.

SystemOwnsVolume answers true on the device -- the build tag, the
constant, the field and the generated binding, end to end, which is the
one thing a source sweep only approximates and which nothing else here
compiles at all.  The control is absent in both mount points on the
real engine, and the transport measures 143px, exactly what the
desktop-headless "after" predicted.  A stored volume of 37 survives a
session that demonstrably rewrote the row.

The duck is the one that stays open, and now for a stated reason rather
than for want of hardware: the foreground service omits
setWillPauseWhenDucked from Oreo, so the framework attenuates us itself
and never sends AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK -- the device logs
`requestAudioFocus() ... flags=0x0` saying so.  minSdk is 21, so that
path is live code on Android 5.0 to 7.1 and unreachable above it.
Asking for a modern phone will not test it.

CLAUDE.md

@@ -1763,7 +1763,8 @@ nothing else. That is `mediacontrols`' split with
 decided against `Player.systemVolume`, a field a test sets either way.
 The frontend's absent branch is therefore testable in the component
 tier with a stubbed binding, and the constant itself is covered by a
-source sweep rather than by a device.
+source sweep plus, once, a real arm64 device answering `true` — which
+is the only tier that compiles the `android` file at all.
 
 **Mute goes with it, because it is a level of zero by another name** —
 and because with no control rendered it is the one state on such a
@@ -1782,6 +1783,14 @@ offset arithmetic exactly as it was. It is the only thing that may move
 the output on such a platform, and it is the one volume-shaped path
 that is not refused.
 
+One thing to know before anyone offers to test it on a phone: **the
+duck is unreachable above API 25.** `WailsForegroundService` builds its
+`AudioFocusRequest` without `setWillPauseWhenDucked` from Oreo, so the
+framework attenuates us itself and never sends
+`AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK` — a device confirms it by logging
+`requestAudioFocus() … flags=0x0`. `minSdk` is 21, so this is live code
+rather than dead, on Android 5.0 to 7.1 and nowhere else.
+
 **And below 600px that bar carries three controls, not five** (#59).
 Shuffle, repeat and the queue button leave it; what is left is art,
 title/artist, favourite, and prev/play/next. `player-controls` is one