[XXX] Future improvements and optimizations

These are nice-to-have improvements marked with XXX comments:

### `play/vue/tootsville-vue/src/views/GameView.vue`
- Line 10:

### `play/Game/Gatekeeper.js`
- Line 125: * XXX bring back passports
- Line 389: // XXX check the datagram layout
- Line 402: // XXX check the params layout
- Line 1051: * XXX @code{d3} objects are ignored. @code{wtl} is the only supported

### `play/Game/Nav.js`
- Line 347: * XXX unclear if this is even used any more?

### `play/Game/Wardrobe.js`
- Line 165: if (!('character' in Tootsville)) return {}; // XXX assert?

### `play/Scene/AvatarBuilder.js`
- Line 66: // XXX rotate only once all the patterns have been recentered on
- Line 214: return; /* XXX finish? */ } }
- Line 264: * XXX keep a cache for identical textures on different avatars, with

### `play/Scene/Patterns.js`
- Line 40: * XXX Some day we might extract these from SVG files.

### `play/Scene/SkyBuilder.js`
- Line 46: * XXX Some day, using a GLSL shader for the background would be
- Line 260: * XXX Some things aren't able to be updated yet.

### `play/Scene/Tank.js`
- Line 43: * XXX This is currently ignored, and we always update the attachments

### `play/UI/AudioControl.js`
- Line 123: // // XXX hide volume controls

### `play/UI/FitSteps.js`
- Line 58: // XXX no op for now

### `play/UI/HUD.js`
- Line 95: { const xhr = new XMLHttpRequest; // XXX: Fetch

### `play/UI/WaWa.js`
- Line 116: { const speed = 9 / Math.min(duration, 9); // XXX adjust speed

### `play/vue/tootsville-vue/pnpm-lock.yaml`
- Line 2487: resolution: {integrity: sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==}
- Line 2487: resolution: {integrity: sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==}

### `www/index.html`
- Line 75:
- Line 80: gtag('config', 'G-XXXXXXXXXX');

### `www/index.qa.html`
- Line 72:
- Line 77: gtag('config', 'G-XXXXXXXXXX');

**Priority:** Low (future enhancements)
**Labels:** enhancement