Use native PiP from the player action

[wizdom13]

• Route the primary PiP-looking player action through Android native picture-in-picture
• Enter PiP without pre-transition fullscreen layout changes so the animation stays smooth
• Keep the legacy floating Popup player as a separate secondary action
• Fall back to Popup when native PiP is unavailable
• Preserve long-press enqueue behavior on the legacy Popup action
• Add regression coverage for the dedicated PiP path
• Fixes PiP transition stutters when using dedicated PiP button, unlike smooth Home button transition #369