fix: reset gesture state on touchcancel

[NemeZZiZZ]

Problem

When the system cancels an in-progress touch gesture (incoming call overlay, notification
shade, palm rejection, browser gesture takeover), a touchcancel event is fired instead of
touchend. Currently it is almost unhandled:

• src/common/EventHandler.ts:692 — a touchcancel listener on the target only clears the
  long-tap timeout.
• The root-level touchmove/touchend listeners (subscribed on touch start, unsubscribed
  on touch end) are not removed on cancel.
• Gesture state (_activeTouchId, _touchMoveStartCoordinate) is not reset, and the chart
  level (Event) never learns the gesture is over.

After a cancelled gesture the handler stays in the "finger down" state: the next touch has
to untangle stale listeners/state, and dragging/scrolling state started on the chart
(_startScrollCoordinate, axis scale state, crosshair) is left dangling — the chart can
keep behaving as if the finger is still down.

Fix

Handle touchcancel symmetrically to touchend:

src/common/EventHandler.ts

• Add touchCancelEvent to the EventHandler interface.
• Add _touchCancelHandler: resolves the active touch, resets _activeTouchId,
  _lastTouchEventTimeStamp, _touchMoveStartCoordinate, unsubscribes the root touch
  listeners, marks the gesture so it cannot resolve into a tap, and dispatches
  touchCancelEvent.
• Subscribe/unsubscribe touchcancel together with touchmove/touchend on the root
  element ({ passive: false }).

src/Event.ts

• Add touchCancelEvent(e): sends mouseUpEvent to the widget under the finger (so
  widgets that started a pressed interaction release it), then unconditionally resets the
  scroll/scale gesture state (same set as touchEndEvent) plus the touch-specific state
  (_touchCoordinate, _touchCancelCrosshair, _touchZoomed) and clears the crosshair.

Unlike touchEndEvent, the state reset is unconditional: on cancel there is no
meaningful "widget under the finger" semantics to gate on, and the point of the handler is
to guarantee a clean slate.

Verification

• pnpm code-lint — pass (154 files, no fixes)
• pnpm type-check — pass
• pnpm build-esm — pass
• Manual: start a drag on a touch device, trigger a system cancel (e.g. notification shade
  pull) mid-gesture — afterwards the chart responds to the next touch immediately and no
  crosshair/scroll state is stuck; on main the same sequence leaves the gesture state
  dangling.

Notes

• Fling inertia is not started on cancel (it only starts in touchEndEvent), so no change
  is needed there.
• The existing target-level touchcancel listener for the long-tap timeout is kept.