[thewhoareyou]

Summary

Closes #6 — matches upstream Moonlight's gesture mapping:

• Three-finger tap toggles the on-screen keyboard (previously opened the menu)
• Four-or-more-finger tap opens the stream menu (previously a fast four-finger tap could also trip it, since the timer started at finger three)
• The floating menu button and holding Select on a controller are unchanged

The tap detector (handleMultiFingerTap) now runs ahead of every mouse/touch mode, so pan/zoom and touch-disabled get the same gestures as the rest, and it consumes the extra fingers so no part of a tap reaches the host. One deliberate behavior change: in multi-touch mode, 3+ finger touches are now claimed by the gesture detector before they can be forwarded to a host with native touch support — the same trade-off upstream makes.

It also fixes a side effect the new gesture exposes: the first two fingers of a tap land before the third and briefly read as a pinch, zooming the stream. The stream view now remembers its state at gesture start (PanZoomHandler.rememberGestureStart/revertToGestureStart), and the extra fingers put it back — including restoring a legitimate zoom left by an earlier pinch rather than resetting it.

Test plan

• GameRulesTest: tap-action matrix (3 -> keyboard, 4/5+ -> menu, slow/short -> none) — 7/7 on JVM
• PanZoomHandlerTest (new, Robolectric): synthesized 2-finger pinch reverts when extra fingers arrive; a zoom from an earlier gesture survives
• lintNonRootDebug clean; assembleNonRootDebug builds
• Device-tested on a Galaxy Tab S9+: three-finger tap toggles the keyboard, four-finger tap opens the menu, and the tap no longer zooms the stream
• Note: tested on a build without the pointer-capture fix in fix(stream-menu): keep the mouse working while the menu is up #4; the changes touch different code paths and merge cleanly

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