Fold the standalone GSplatParams#debugAabbs and GSplatParams#debugNodeAabbs boolean flags into the existing GSPLAT_DEBUG_* enum-based debug property, for a single, consistent way to pick a gsplat debug mode. The old flags are retained as deprecated shims.

Changes:

• Add GSPLAT_DEBUG_AABBS and GSPLAT_DEBUG_NODE_AABBS enum values.
• Remove the debugAabbs / debugNodeAabbs boolean fields from GSplatParams.
• Consumers in GSplatManager and GSplatOctreeInstance now check debug === GSPLAT_DEBUG_*.
• Expose the two new modes in the Debug dropdown of the world, lod-streaming, and lod-streaming-sh gsplat examples.

API Changes:

• Added: GSPLAT_DEBUG_AABBS, GSPLAT_DEBUG_NODE_AABBS.

• Deprecated: GSplatParams#debugAabbs, GSplatParams#debugNodeAabbs — these now forward to debug and emit a deprecation warning. Migration:

  // before
  app.scene.gsplat.debugAabbs = true;
  app.scene.gsplat.debugNodeAabbs = true;
  
  // after
  app.scene.gsplat.debug = pc.GSPLAT_DEBUG_AABBS;
  app.scene.gsplat.debug = pc.GSPLAT_DEBUG_NODE_AABBS;

Examples:

• gaussian-splatting/world, gaussian-splatting/lod-streaming, gaussian-splatting/lod-streaming-sh: Debug dropdown now includes AABBs and Node AABBs.