…nings) (#8803)

Follow-up cleanups to #8802 (flip of GSplatComponent#unified default to
true). Addresses spurious deprecation warnings raised by engine-internal
code, and updates the bundled orbit-camera script to be unified-aware.

- GSplatComponent: route internal mesh-instance probes through the
  private _instance field instead of the deprecated public instance
  getter (set castShadows, addToLayers, removeFromLayers).
- GSplatComponent: silence the spurious Debug.errorOnce in
  onLayerAdded / onLayerRemoved. These are engine-driven event handlers
  subscribed to the layer composition's add/remove events — not
  user-facing APIs — so they now silently no-op in unified mode.
- scripts/camera/orbit-camera.js: _buildAabb now collects AABBs for
  unified gsplats via gsplat.customAabb transformed by the entity's
  world matrix, so unified gsplats contribute to the orbit camera's
  focus AABB instead of being silently skipped.
- examples/.../global-sorting.example.mjs: now that the orbit camera
  correctly builds an AABB for unified gsplats, the prior framing
  (which incidentally relied on an empty AABB at origin) needed an
  explicit pivot — switched to resetAndLookAtPoint targeting the
  statue's world-space centre.

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

)

The legacy gsplat picking example documents itself as "using legacy
(non-unified) mode" but its addComponent('gsplat', { ... }) calls never
specified unified: false. After #8802 flipped the default to true, the
example was silently created in unified mode and crashed in its click
handler when it accessed gsplat.instance.meshInstance (instance is null
in unified mode).

Adding unified: false restores legacy mode as the example documents,
and produces exactly the one expected DEPRECATED: GSplatComponent#unified
warning on startup — the intended migration signal from #8802.

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

Follow-up cleanup to the unified-default flip (#8802, #8803, #8804).
Unified rendering is now the default and the unified property is
@deprecated/@ignore, so the public API docs and examples shouldn't be
framed around "unified mode" any more — it's just gsplat rendering.

Engine source:
- GSplatComponent: remove the "## Unified Rendering" section from the
  class JSDoc; strip the JSDoc blocks from material get/set and
  highQualitySH get/set (both are legacy-only and only documented the
  unified/non-unified distinction). Drop "unified" qualifiers from
  workBufferUpdate, workBufferModifier, setParameter, and
  getInstanceTexture JSDocs.
- GSplatComponentSystem: drop "in unified mode" from the
  material:created and frame:ready event JSDocs, and from the
  getMaterial JSDoc.
- GSplatParams: rename "Parameters for GSplat unified system" to
  "Parameters for the GSplat system"; drop "unified" qualifier from
  dataFormat, material, and format JSDocs.
- GSplatContainer: drop "non-unified rendering" from the class example
  comment, drop unified: true from the addComponent example, drop
  "unified" qualifier from the centers JSDoc.

Examples (gaussian-splatting folder):
- Remove unified: true from every addComponent('gsplat', { ... }) call
  (~40 occurrences across 29 files) — it's now the default and the
  property is deprecated.
- Reword/remove comments that mention "unified" framing now that it's
  just the standard path (e.g. "Create hotel gsplat with unified set
  to true" → "Create hotel gsplat").
- Drop three stale orbit-pivot comments ("unified gsplats have no mesh
  AABB for focusEntity framing") — these became factually incorrect
  once #8803 made orbit-camera unified-aware.
- Update global-sorting example header from "demonstrates unified
  gsplat rendering" to "demonstrates global gsplat sorting" to reflect
  what the example actually shows.

Remaining "unified" mentions in the engine are all either internal
(private fields, code comments, code branches), runtime warning strings
(which must keep the property name), @ignore'd JSDoc, or directory
names — none render in public docs.

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>

Follow-up cleanup to the unified-default flip (#8802, #8803, #8804).
Unified rendering is now the default and the unified property is
@deprecated/@ignore, so the public API docs and examples shouldn't be
framed around "unified mode" any more — it's just gsplat rendering.

Engine source:
- GSplatComponent: remove the "## Unified Rendering" section from the
  class JSDoc; strip the JSDoc blocks from material get/set and
  highQualitySH get/set (both are legacy-only and only documented the
  unified/non-unified distinction). Drop "unified" qualifiers from
  workBufferUpdate, workBufferModifier, setParameter, and
  getInstanceTexture JSDocs.
- GSplatComponentSystem: drop "in unified mode" from the
  material:created and frame:ready event JSDocs, and from the
  getMaterial JSDoc.
- GSplatParams: rename "Parameters for GSplat unified system" to
  "Parameters for the GSplat system"; drop "unified" qualifier from
  dataFormat, material, and format JSDocs.
- GSplatContainer: drop "non-unified rendering" from the class example
  comment, drop unified: true from the addComponent example, drop
  "unified" qualifier from the centers JSDoc.

Examples (gaussian-splatting folder):
- Remove unified: true from every addComponent('gsplat', { ... }) call
  (~40 occurrences across 29 files) — it's now the default and the
  property is deprecated.
- Reword/remove comments that mention "unified" framing now that it's
  just the standard path (e.g. "Create hotel gsplat with unified set
  to true" → "Create hotel gsplat").
- Drop three stale orbit-pivot comments ("unified gsplats have no mesh
  AABB for focusEntity framing") — these became factually incorrect
  once #8803 made orbit-camera unified-aware.
- Update global-sorting example header from "demonstrates unified
  gsplat rendering" to "demonstrates global gsplat sorting" to reflect
  what the example actually shows.

Remaining "unified" mentions in the engine are all either internal
(private fields, code comments, code branches), runtime warning strings
(which must keep the property name), @ignore'd JSDoc, or directory
names — none render in public docs.

Co-authored-by: Martin Valigursky <mvaligursky@snapchat.com>