docs: promote "Build for Mobile" to top-level section + new pages

[rodrigo685]

Summary

Promotes Build for Mobile to a top-level navigation section, relocates all files to creator/build-for-mobile/, restructures into three sub-sections (Mobile Client / Develop / Publish), and adds several new reference pages. Also removes outdated copy and TestFlight beta references.

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1. Promote "Build for Mobile" to top-level section + relocate files

• Removed "Building for Mobile" from being nested under Scenes (SDK7)
• All files moved from creator/sdk7/building-for-mobile/ to creator/build-for-mobile/ to match the path pattern of other top-level categories (wearables-and-emotes/, scene-editor/, 3d-modeling/)
• Restructured into three sub-sections: Mobile Client, Develop, Publish
• creator/SUMMARY.md updated accordingly

2. Remove outdated tip from Onscreen UI (creator/sdk7/2d-ui/onscreen-ui.md)

• Removed the sentence: "A useful starting point is to design your UI on desktop and then scale sizes by 3× for mobile readability."

3. Add Hardware Requirements page (creator/build-for-mobile/mobile-client/hardware-requirements.md)

• Android and iOS minimum/recommended specs tables (accurate as of April 2026)

4. Remove TestFlight references

• Removed beta tester TestFlight callout from creator/sdk7/building-for-mobile/README.md + added mobile app screenshot
• Removed beta tester TestFlight callout from player/mobile-app/README.md + added mobile app screenshot

5. Add Missing Features page (creator/build-for-mobile/mobile-client/missing-features.md)

• Tracks the feature gap between the desktop (Unity) client and the mobile app
• Sourced from the godot-explorer feature parity tracker
• Sections: SDK Features Missing on Mobile, Desktop Client Features Not in Mobile, Cross-Platform Inconsistencies, Input/Platform Constraints
• Smart Items noted as unconfirmed on mobile, ETA August 2026

6. Add Sample Scenes page (creator/build-for-mobile/mobile-client/sample-scenes.md)

• Open-source mobile-optimized scenes from dcl-regenesislabs: Dead Surge, Cozy Farm, Kick Off, Raft Game, Venetian Hunt, Tower of Madness

7. Add Optimize Performance page (creator/build-for-mobile/develop/optimize-performance.md)

• Mobile scene limits table (12 metrics) — Performance soft limit 90%, hard limit 80%
• Preview Mobile Performance section: how to access Scene Limits Preview in Creator Hub via QR code
• Single warning hint consolidating: Performance metric explanation, 90% target on High Graphics on Samsung Galaxy A54, and how to switch Graphic Profiles (In-Game Menu → Settings → Graphics)

8. Add Mobile Client section with Overview page (creator/build-for-mobile/mobile-client/)

• Overview page with download links, section map (Reference / Develop / Publish), and quick checklist
• Quick checklist includes: device preview, safe area, UI sizing, input bindings, and 90% Performance on High Graphics Profile

9. Add Develop and Publish section indexes

• develop/README.md — index linking Detect Platform, Preview on Mobile, Safe Area, UI Best Practices, Input on Mobile, Performance
• publish/README.md — intro clarifying the standard publishing flow still applies (link to SDK7 Publishing guide); Get Featured and iOS Curation are additional steps on top

10. Add image to Get Featured page

• Added mobile-featured.png below the intro paragraph in creator/build-for-mobile/publish/get-featured.md

11. Address review feedback (nearnshaw)

• detect-platform.md: rewrote opening paragraph to lead with isMobile() instead of giving prominence to the module path
• missing-features.md: removed bold formatting from "Smart Items" and "Marketplace Credits" entries (no link → looked visually special); updated Smart Items note with ETA
• publish/README.md: added intro paragraph making clear the standard publish flow is required first

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New file structure

creator/build-for-mobile/
├── mobile-client/
│   ├── README.md
│   ├── overview.md
│   ├── sample-scenes.md
│   ├── missing-features.md
│   └── hardware-requirements.md
├── develop/
│   ├── README.md
│   ├── detect-platform.md
│   ├── preview-on-mobile.md
│   ├── safe-area.md
│   ├── ui-best-practices.md
│   ├── input-on-mobile.md
│   └── optimize-performance.md
└── publish/
    ├── README.md
    ├── get-featured.md
    └── ios-curation.md

Images (repo root)

File	Used in
mobile-app-screenshot.png	overview.md
mobile_scene_limits.png	optimize-performance.md
mobile-featured.png	get-featured.md

[nearnshaw]

I think we need here some mention of the fact that you still have to go through the normal publishing process to upload the scene, via the CH or the CLI. Including a link to https://docs.decentraland.org/creator/scenes-sdk7/publishing/publishing

The steps described in this section are in addition to the actual publishing of the scene
But the way the topics are organized can lead you to think that for Mobile scenes you follow an entirely separate flow that doesn't include what's described in the /publishing section under Scenes(SDK7)