[General] Align `pointerType` across native and JS (#4403)

## Description

The JS `PointerType` enum is `TOUCH, STYLUS, MOUSE, KEY, OTHER`, but the
native constants stopped at `OTHER = 3` — the value JS reads as `KEY`.
Native pointer types travel to JS as plain ints with no translation
layer
(`gestureHandlerCommon.ts` types them as `PointerType`), so every native
"other pointer" surfaced as `PointerType.KEY`, and `PointerType.OTHER`
was
unreachable from native. It is reachable on Android through
`TOOL_TYPE_ERASER` / `TOOL_TYPE_UNKNOWN`, and on Apple through tvOS
focus-driven hover and any touch that is neither direct, pencil, nor
indirect pointer.

Declares `KEY` on both platforms so `OTHER` lands on 4. Native never
emits
`KEY` — it is produced only by the web `KeyboardEventManager`.

With the values consistent, `ButtonEvent.pointerType` is narrowed from
`number` to `PointerType`. It only mirrored the codegen spec's `Int32`;
the
spec keeps its own self-contained copy, so codegen is unaffected.
Numeric
enums and `number` are mutually assignable, so this breaks no consumer —
which is also why the `buttonEventTest` drift guard still passes. That
guard
can no longer tell a deliberate refinement of this field from real spec
drift, but it still catches added, removed and retyped fields.

## Test plan

- Android: `:react-native-gesture-handler:compileDebugKotlin` and
  `:app:assembleDebug` in `apps/basic-example/android` both succeed
- Apple: enum values pinned by a compiled assertion (`Touch` 0 … `Key`
3,
`OtherPointer` 4); no `switch` over the enum exists, so no `-Wswitch`
fallout
- `yarn ts-check` clean (both passes), `yarn test` 115/115, `yarn
lint:js`
  0 errors
- The iOS app build was not run — `pod install` fails on this machine
for
  reasons unrelated to the change (rvm `libruby.2.7.dylib` mismatch)