fix(cua-driver): route interactive macOS scroll events

[f-trycua]

Summary

• route low-latency macOS wheel events through the existing PID/window-stamped native paths
• preserve real trackpad pixel phases and momentum
• convert phase-less precise wheel samples into proportional line motion instead of silently dropping them in Chromium
• share the routing primitive with the existing one-shot scroll implementation

Root cause

CoreGraphics accepted foreground HID wheel events, but Chromium could silently ignore them because they lacked the target PID and window-routing fields. Phase-less high-resolution wheel events were also ignored when posted as continuous pixel gestures.

Impact

Stateful interactive scroll sessions now work across Chromium and native AppKit targets without the sleeps or per-tick replay used by automation-oriented scroll tools.

Validation

• cargo test -p platform-macos (155 passed)
• signed macOS live test against a Chromium window: a phase-less precise sample moved the target view with 12.5 ms native dispatch