fix(tao): dispatch recognized trackpad pinch as Compose Scale events (#660)

[kdroidFilter]

Closes #660.

Platform-recognized pinch (AppKit magnify, GDK pinch, Windows Ctrl+wheel) was replayed as two synthetic PointerType.Touch contacts 120 px either side of the cursor. That sent an already-recognized gesture through Compose touch recognition again: span/slop delay, release momentum, and contacts that could miss the target or hit neighbouring chrome (the MapLibre edge interruptions).

What changed

• Magnify is now ScaleStart / ScaleChange / ScaleEnd at the cursor, with scaleGestureFactor as the per-event ratio (1 + NSEvent.magnification, GDK's ratio, or the Windows/Linux Ctrl+wheel step).
• Shared dispatchTrackpadScale + TaoTrackpadScaleSession (same shape as the Tao: distinguish trackpad panning from wheel scrolling in Compose #654 pan path).
• Rotation still synthesises two Touch pointers — Compose has no rotation event.
• ZoomTab and Trackpad Lab consume Scale events; the inspector logs them.

Measured on the offscreen Tao scene (macOS, same ComposeScene as the host):

	Two-touch synthesis	Scale events
Pointers	2 Touch, ±120 px, span 240 px	1 Mouse at the cursor
Map edge (cursor 10 px inside)	one contact in the map, one in chrome	map only
+1 % pinch	0 detectTransformGestures callbacks (zoomMotion 1.2 px vs ~18 px slop)	transformable zoom = 1.01 immediately
Delay	13 × 1 % steps (~13 %) before zoom	none

detectTransformGestures does not see Scale events (Compose 1.12). Apps that pinch via that API need Modifier.transformable or a PointerEventType.Scale* listener — MapLibre already does.

Test plan

• :decorated-window-tao:test — TaoSceneTrackpadScaleTest, TaoTrackpadScaleSessionTest
• :examples:shared:compileKotlin / :examples:nucleus-demo:compileKotlin
• ktlint + detekt on the touched modules
• Trackpad Lab: pinch logs ScaleStart / ScaleChange / ScaleEnd, map canvas zooms, two-finger swipe still pans
• ZoomTab: pinch zooms, two-finger rotate still rotates

[sargunv]

confirmed this works well with maplibre compose