- Add GestureInputMode enum (.mouseMovement / .scrollWheel) to GestureBinding with backward-compatible Codable (old JSON without key defaults to .mouseMovement)
- Add handleScrollEvent() to GestureProcessor: consumes scroll events in both .pending (accumulate delta, resolve direction) and .active (prevent smooth-scrolling pipeline leak) states
- Guard handleMotionEvent and startGestureTracking to only run for .mouseMovement bindings
- Hook GestureProcessor.handleScrollEvent into ScrollCore.scrollEventCallBack before trackpad check
- Fix footer layout: deactivate conflicting storyboard constraints and repin +/- buttons to trailing edge so segmented control doesn't overlap them
- Add right-click context menu delete to GestureTableCellView
- Add input mode segmented control (Movement / Scroll) to GestureTableCellView with onInputModeChanged callback
- Wire updateGestureInputMode() in PreferencesButtonsViewController
- Add gestureMouseMovement, gestureScrollWheel, delete localization keys (en/zh-Hans/zh-Hant/ja)
- Add 11 new unit tests covering scroll gesture state machine, backward-compatible Codable, and active-state scroll leak prevention

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…irection only

Movement (↑↓←→) and Scroll (↑↓) are now separate, simultaneously active configs
on the same gesture binding — remove the single-mode toggle entirely.

- GestureBinding: remove GestureInputMode enum and inputMode field; add
  scrollUpAction/scrollDownAction/scrollThreshold fields; manual encode(to:)
  skips legacy inputMode key; backward-compatible decoder ignores old inputMode
- GestureProcessor: independent pendingScrollDY accumulator (separate from motion
  DX/DY); handleScrollEvent uses scrollAction(for:) and scrollThreshold;
  handleMotionEvent guards on hasAnyMovementAction; motion tap only started when
  binding has movement actions; pendingScrollDY reset on all pending→idle transitions
- GestureTableCellView: remove inputMode segmented control; show two labeled
  sections side-by-side (Movement 4-dir, Scroll 2-dir); separate popup/action
  selectors and callbacks for each section
- PreferencesButtonsViewController: replace updateGestureInputMode with
  updateGestureScrollAction; wire onScrollActionChanged callback; row height 150
- Localizable.xcstrings: rename gestureMouseMovement→gestureMovement,
  gestureScrollWheel→gestureScroll (section header labels)
- GestureProcessorTests: update helpers, replace inputMode tests with
  threshold/scroll-action tests, add accumulator-independence test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Two root causes:

1. Silent event consumption: when scrollDownAction is nil but scrollUpAction
   is set, hasAnyScrollAction=true caused all scroll-down events to be consumed
   (returning true) without any action firing. User saw no scrolling and no action
   — perceived as "scroll conflict".

   Fix: direction-aware consume. Check binding.scrollAction(for: eventDirection)
   before accumulating. If nil for that direction, immediately return false
   (let scroll pass through normally). Reset accumulator on direction change.

2. Smooth-scroll mouse delta: reading scrollWheelEventDeltaAxis1 (integer) gives 0
   for continuous/smooth scroll devices. No accumulation → threshold never reached.

   Fix: prefer scrollWheelEventFixedPtDeltaAxis1 (float fixedPt field, same
   priority logic as ScrollEvent.initEvent), fall back to integer field.

Both pending and active states updated to use the same direction-aware logic.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…hold

Previously, after a scroll gesture fired the state became .active and all
subsequent scroll events in configured directions were consumed without firing.
This caused a 5+ second apparent freeze: the user had to fully release the
trigger button before the other direction would work again.

Fix: in .active state, scroll gestures now re-fire on every threshold crossing.
Hold button + scroll up → fires, scroll down → fires, scroll up → fires again.
Directions with no configured action still pass through immediately.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>