feat: add scene content stats to the Current Scene debug widget

[dalkia]

Pull Request Description

What does this PR change?

Adds per-scene content statistics to the "Current scene" debug widget so creators and devs can see, at a glance, how close the scene they are standing in is to its limits. Nine new rows appear at the top of the widget, each formatted current / maxcap (pct%) and colored green (< 80%), yellow (80–99%) or red (≥ 100%):

• Entities — live CRDT entities (EntitiesMap.Count)
• Triangles — summed from primitive mesh renderers + GLTF container renderers
• Meshes (bodies) — renderer count (primitive + GLTF)
• Geometries — unique Mesh instances
• Materials / Textures — unique instances, deduped across SDK materials and GLTF-embedded materials (textures probed from common shader properties)
• Colliders — primitive colliders + GLTF invisible/decoded-visible colliders
• Content size — runtime memory of the scene's unique meshes + textures (Profiler.GetRuntimeMemorySizeLong); there is no per-scene downloaded-bytes accumulator, so deployed size is not knowable at runtime
• External content — media streams not served from the content server + NFT shapes

Caps are hardcoded from the documented Decentraland scene limitations, scaled by parcel count n: triangles n×10000, entities n×200, bodies n×300, materials log2(n+1)×20, textures log2(n+1)×10, geometries log2(n+1)×200, content size 15MB×n. Colliders (n×300) and external content (10) have no documented limit, so they use project-chosen constants. All caps live in one constants block in DebugViewCurrentSceneSystem.Formatting.cs.

Architecture: a new scene-world system (SceneContentStatsSystem, SyncedPresentationSystemGroup) counts every 30 frames and writes into a new SceneContentStats payload on SceneRuntimeMetrics (now exposed to scene-world systems via ECSWorldInstanceSharedDependencies). The global DebugViewCurrentSceneSystem sets a CollectionRequested demand flag only while the widget is expanded on the current scene — with the debug panel closed or disabled, the scene system does a single bool check per frame and nothing else. Counting is allocation-free (reused HashSets / scratch list, non-alloc GetSharedMaterials).

Test Instructions

Steps (standard run):

metaforge explorer run 9457

Expected result:
The "Current scene" debug widget shows the nine new stat rows with colored current / max (pct%) values for the scene you are standing in.

Steps (fresh account):

metaforge account create --clear
metaforge explorer run 9457

Expected result:
Same as above after finishing onboarding.

Automation (if applicable):
N/A

Prerequisites

• Run with the debug panel available (editor play mode or a build with --debug)

Test Steps

1. Enter any world/scene and open the debug panel
2. Expand the "Current scene" widget
3. Rows show "—" for up to ~1 second, then populate with current / max (pct%) values colored green/yellow/red
4. Walk into a neighboring scene — values reset and repopulate for the new scene, and caps change with the scene's parcel count
5. Collapse the widget or close the panel — values freeze (collection stops); reopen and they refresh within a second
6. Visit a heavy scene (e.g. Genesis Plaza) and verify triangle/material counts move into yellow/red

Additional Testing Notes

• "Content size" measures runtime memory of unique meshes + textures, not the deployed bundle size — the 15MB/parcel cap is indicative
• GLTF stats only count containers in Finished state, so values grow while a scene streams in
• Empty/loading scenes show "—" until the first collection pass
• No SDK behavior changes — this is debug-panel-only

Quality Checklist

• Changes have been tested locally
• Documentation has been updated (if required)
• Performance impact has been considered
• For SDK features: Test scene is included

Code Review Reference

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🤖 Generated with Claude Code

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Tests: 23922 passed, 0 failed ✅