feat(android): the tap highlight goes, a press state replaces it

The phone drew a grey box over the bounding rect of whatever was
tapped, which is the web view saying what it is. It is gone in one
declaration: `-webkit-tap-highlight-color` is inherited and an
inherited property crosses a shadow boundary, so `html` in index.css
reaches every shadow root in the app. Measured three roots deep,
rgba(0, 0, 0, 0.18) before and rgba(0, 0, 0, 0) after.

Removing it removes the only touch feedback several surfaces had, so
the press state is part of the same change rather than a later polish
item — with the highlight gone a held row measured the *hover* tint,
which on a phone is synthesised by the hold itself and outlives it.
The four lists' rows, the tab bar, the sidebar's destinations and the
shared context-menu item take --yj-press-overlay on :active; the cards
already had scale(0.97). The press selector carries a state class
because a row is .track-row.selected.active, so a bare :active shows
nothing on the row a phone is most likely to press. And those
surfaces' hover tints move behind (hover: hover) and (pointer: fine),
which is #68's gate applied to a tint rather than a revealed control.

user-select, the other half of the Findings, was already done: the
first rule in index.css covers the shadow roots for the same reason.
touch-action: manipulation is declined — the 300ms delay it is offered
for is already absent on a width=device-width viewport, and what it
would really change is the gesture stack tuned by measurement on a
device this session cannot measure.

Closes #54

frontend/src/components/queue-panel/queue-panel.ts

@@ -581,8 +581,14 @@ export class QueuePanel
             contain: strict;
         }
 
-        .track-item:hover {
-            background-color: var(--yj-hover-overlay, rgba(255, 255, 255, 0.05));
+        /* A hover tint is for a device that hovers (#54). A hold
+           synthesises a hover in the WebView, so ungated this arrives
+           because a finger touched the row and stays after it has
+           gone; the press state below is what a tap gets instead. */
+        @media (hover: hover) and (pointer: fine) {
+            .track-item:hover {
+                background-color: var(--yj-hover-overlay, rgba(255, 255, 255, 0.05));
+            }
         }
 
         .track-item.selected {
@@ -597,6 +603,19 @@ export class QueuePanel
             background-color: var(--yj-selection-bg, rgba(100, 160, 255, 0.15));
         }
 
+        /* The press state (#54): the feedback a tap has now that the
+           web view's own highlight box is gone (index.css). Last, and
+           carrying a class, because a selected or playing row is two
+           classes deep and a bare :active would lose to it. */
+        .track-item.selected:active,
+        .track-item.active:active,
+        .track-item:active {
+            background-color: var(
+                --yj-press-overlay,
+                rgba(255, 255, 255, 0.12)
+            );
+        }
+
         .track-position {
             font-size: var(--yj-text-sm);
             color: var(--yj-text-tertiary, #888);