feat(android): swipe a track row right to queue it

Plan 019 phase 2. A finger on a track row now drags a reveal out from
under it and queues the track on release, with the affordance saying
what it will do before it does it.

Two things the device said that the plan did not predict, and both
change the implementation rather than decorate it.

The gesture runs on touch events, not pointer events. Chrome 113's
WebView cancels the pointer stream ~16px into any drag whatever
touch-action says -- measured at auto, pan-y and none alike -- while
touchmove keeps firing. So touch-action: pan-y is half the fix and a
non-passive touchmove calling preventDefault is the other half, and
neither works alone: with the preventDefault in place and touch-action
back at auto the gesture died after one move. Both are correct in
Chromium either way, which is why the module's header carries the
measurement and the component tier asserts the stylesheet.

And a phase 1 defect the device found on the way past: the native
contextmenu arrives in either order and only one was handled. Our
500ms timer firing first, a component claiming it, and Chrome
delivering its own menu 50-70ms later was suppressed by nothing -- so
the context menu opened over the selection bar, two holds in four, on
the one surface this issue exists to have changed. Six holds clean
after.

draggable="true" is not a competitor: no dragstart fires from a touch
drag on this WebView at all.

.planning/plans/active/019-android-touch-model.md

@@ -225,7 +225,8 @@ still works. `SelectionController` gains a mode. `track-list` acts on
 tap and enters the mode on long press. The action bar.
 
 **Phase 2 — swipe right to queue**, with the `touch-action: pan-y`
-finding above and a reveal-and-snap affordance.
+finding above and a reveal-and-snap affordance. **Shipped**; what the
+device said about it is the section below.
 
 **Phase 3 — the other three surfaces**, which is mostly wiring, since
 they already share the controller.
@@ -237,6 +238,94 @@ beyond making tap-to-play win on touch.
 
 ---
 
+## What phase 2 measured, which was not what phase 2 predicted
+
+The `touch-action` finding above is **half** of the answer, and
+shipping only that half would have been the exact failure it warns
+about. Driving a real finger with `adb shell input swipe` across a
+track row, three values, all three on the device:
+
+```
+touch-action: auto    pointerdown, 1 move,  pointercancel
+touch-action: pan-y   pointerdown, 2 moves, pointercancel
+touch-action: none    pointerdown, 2 moves, pointercancel
+```
+
+`touchmove` kept firing in all three. So **Chrome 113's WebView
+cancels the pointer stream ~16px into any drag whatever `touch-action`
+says**, and a swipe recognised from `pointermove` — which is what the
+rest of this module is built on — is a swipe that dies 16px in.
+
+The other half is a **non-passive `touchmove` calling
+`preventDefault()`**: with it, the same swipe ran to 12 moves and a
+`pointerup` at full travel. And both halves are required, which was
+measured rather than assumed — with the `preventDefault` in place and
+`touch-action` back at `auto`, the gesture died after **one** move.
+The reading is that `auto` lets the browser commit to a horizontal pan
+on the first move past slop, before any threshold of ours can have
+been crossed, while `pan-y` leaves it undecided long enough for the
+second move to claim it.
+
+`none` is the one value to avoid: the list stopped scrolling at all.
+With the shipped pair, a vertical drag still scrolls the virtualizer
+81px on the same run that a horizontal one survives.
+
+**`draggable="true"` is not a competitor**, which is the other thing
+the device was asked. No `dragstart` fires from a touch drag on this
+WebView at all, so the drag-to-playlist attribute on every row needs no
+pointer-type gate.
+
+### And it found a phase 1 defect that no tier can see
+
+The native `contextmenu` arrives in **either** order, and phase 1 only
+handled one of them. `nativeSeen` covers the browser's menu arriving
+*during* the hold. The reverse — our 500ms timer firing first, a
+component claiming it, and Chrome delivering its own `contextmenu`
+50–70ms *later* — was suppressed by nothing, so the context menu
+opened on top of the selection bar. Measured over four holds:
+
+```
+hold 1  yj-long-press, then contextmenu isTrusted=true   menu open
+hold 2  yj-long-press                                    clean
+hold 3  yj-long-press, then contextmenu isTrusted=true   menu open
+hold 4  yj-long-press                                    clean
+```
+
+Two in four, on the one surface #63 exists to have changed, and
+invisible to both browser tiers because neither synthesises a
+`contextmenu` from a dispatched press. A press that has produced its
+outcome now suppresses a late one whichever branch it took; six holds
+on the fixed build, six clean.
+
+### The rules phase 2 settled
+
+- **A swipe is not a selection.** It queues the row it was made on,
+  unless that row is one of several *explicitly* selected — the same
+  rule the context menu answers with, because a bar reading "40
+  selected" beside a gesture that quietly queues one of them is two
+  answers to one question. It never changes the selection, which is
+  where it differs from a right-click.
+- **Rightward only.** Nothing is bound to a leftward swipe and
+  claiming one would take a gesture away to do nothing with it.
+- **The commit threshold is a fraction of the row** (0.3, floor 72px),
+  because the row is 424x52 on this device and a bare pixel count is a
+  fraction of a row height on one screen and a third of the width on
+  the next.
+- **The affordance is not only a colour** (WCAG 1.4.1, the rule the
+  playing-row marker exists for): the pane carries the queue icon and
+  words, the words change at the threshold ("Add to queue" → "Release
+  to add" → "Added"), and the outcome is announced in a live region.
+- **The row does not move; its cells do.** `.track-row` is
+  `contain: strict` with `overflow: hidden`, so a pane held at the
+  row's original position while the row translates is a pane at a
+  negative offset inside a clipping box and is simply not painted.
+  Sliding the cells needs no wrapper element in a row that is already
+  a grid.
+- **The travel is written to the row's own style, not rendered.** One
+  render at the start, one at the threshold, one at the end; a
+  virtualizer re-rendering every visible row per frame of one finger's
+  travel is the thing `perf.m1` is about.
+
 ## Open questions
 
 1. **Does selection mode have an escape other than the bar's own