Add shared haptics helper and mobile vibration fallback in api/xr.js

[tracygardner]

Motivation

• Provide a single shared haptics entrypoint to centralize gamepad haptics and a mobile vibration fallback in api/xr.js.
• Ensure existing controller rumble APIs behave sensibly on phones by mapping gamepad motors/patterns to the Vibration API when no gamepad actuator is available.

Description

• Added a new helper triggerHaptics that attempts gamepad haptics via vibrationActuator.playEffect("dual-rumble", ...) first, and falls back to navigator.vibrate(...) if no suitable actuator is found.
• Refactored controllerRumble to call triggerHaptics and map mobile behavior to a single vibration duration (ignoring left/right motors on phones).
• Refactored controllerRumblePattern to build scheduled gamepad effects and a corresponding vibration array ([on, off, on, off, ...]) for the mobile fallback.
• Refactored playRumblePattern to convert entries in rumblePatterns (using each pulse's duration and pauseAfter) into both gamepad effects and a vibration-array timing for navigator.vibrate, while keeping behavior noop-safe when neither API is available.

Testing

• Ran node --check api/xr.js which completed without errors.

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Codex Task