Version 4.0.0 - Refactor Trackpad API

[unhuman]

fix: Replace CGEvent tap with IOHIDManager for physical click detection

- Physical click detection now uses IOHIDManager, which receives actual hardware button-press events at the kernel HID layer. Three Finger Drag synthesises leftMouseDown events at the CGEvent/accessibility layer and is therefore completely invisible to IOHIDManager — TFD now works alongside MiddleClick without conflict.

- Remove CGEventController and the CGEvent tap (Controller+Mouse.swift). wasLeftConverted, wasRightConverted, physicalClickArmed, and lastClickTime are removed from GlobalState. HIDClickHandler synthesises otherMouseDown/Up directly, rather than intercepting and mutating existing events.

- HIDClickHandler gates conversion on a 60 ms stable contact window (threeDownSince, re-added to GlobalState) to filter pressure-deformation transients during 2-finger clicks, matching the original arming intent.

- Fix tap-to-click false positives: remove the 'early lift' promotion in TouchHandler (armed → stableArmed when count drops after ≥ 50 ms). The qualifying finger count must now remain stable until all contacts lift together, preventing a slow 3-finger scroll or resting thumb from accidentally arming a middle click.

- Remove Three Finger Drag from the conflict detection alert (Controller+Conflicts.swift) since TFD is no longer a conflict.

- Update docs/three-finger-drag.md and docs/CHANGELOG.md.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>