Add Streamed SOG and Voxel format specs, fix splat doc errors, adopt "Streamed SOG" terminology

[slimbuck]

Overview

Makes the developer site the canonical home for the splat-transform format specs and
guides, documents the newly finalized Streamed SOG format, fixes accuracy errors in
the SOG spec and the Streamed SOG guide, and renames "LOD streaming" to "Streamed SOG"
across the docs. All changes are mirrored in the Japanese translations.

Companion splat-transform PR deletes the duplicated guides/ folder from that repo and
repoints its README here — this PR must deploy first so those links resolve.

New: Streamed SOG format specification

• New page: user-manual/gaussian-splatting/formats/streamed-sog (en + ja), following
  the SOG spec's structure (file set → meta interface → tree semantics → example →
  versioning).
• Specifies lod-meta.json v1: version, asset.generator, count/counts, optional
  environment, filenames, and the spatial tree, plus previously undocumented
  semantics (leaf bounds include Gaussian extents, LOD 0 = highest detail,
  offset/count splat ranges with per-run Morton order, pre-versioning compatibility).
• Added to the sidebar and the Splat File Formats index (now three formats, with
  comparison table and workflow updates).

Matches the lod-meta.json output finalized in the companion splat-transform change.

New: Voxel format specification

• New page: user-manual/splat-transform/voxel-format (en + ja), ported from the
  splat-transform repo's VOXEL_FORMAT.md — previously the only format spec without a
  developer-site home.
• Collision guide now links it again (the on-disk-structure reference was dropped when
  the spec had nowhere to point on this site) and gains a "See also" entry.

Fixed: SOG spec accuracy (verified against splat-transform and engine source)

• Scales codebook is log-domain — decode requires exp(); previously documented as
  linear-space, which would produce garbage sizes if implemented as written.
• Quaternion component order — the smallest-three decode is (w, x, y, z) ordered;
  now stated explicitly, and the mode case comments were off by one position
  (mode 0 = w omitted … mode 3 = z, not x…w).
• antialias is now optional — no writer emits it, so as written every shipped SOG
  file was non-conformant.
• The ja SOG spec also gained the missing asset field (it predated that addition).

Fixed: Streamed SOG guide accuracy (verified against engine source)

• "octree" → "spatial tree" — the format's tree is binary, not an octree (the term
  leaked from the engine's GSplatOctree class name). The resource?.octree?.lodLevels
  code snippet is unchanged since that's the literal API property name.
• lodMultiplier default corrected to 3, clamped to ≥ 1.2 (was documented as 2).
• The ja guide was synced to current en content (it still documented the removed
  lodDistances API).
• Fixed a pre-existing ja broken anchor by giving the ja performance page an explicit
  {#global-splat-budget} anchor.

Renamed: "LOD streaming" → "Streamed SOG"

Across 11 en + 10 ja pages (building guide, performance, rendering architecture,
splat-transform, SuperSplat pages, pc-splat reference, tutorial). Deliberately unchanged:

• URL slugs (/building/lod-streaming, tutorial slug) — avoids breaking inbound links;
  titles and sidebar labels now read "Streamed SOG".
• <EngineExample> ids and the {#generating-lod-format} explicit anchor.

Verification

• docusaurus build succeeds for en and ja with no broken links; the only remaining
  broken-anchor warning (managing-scripts) predates this PR and is unrelated.
• markdownlint clean on all touched files.

[Copilot]

Pull request overview

Adds documentation for the finalized Streamed SOG format, corrects several accuracy issues in the existing SOG specification, and updates docs to consistently use “Streamed SOG” terminology (with mirrored Japanese translations).

Changes:

• Added new Streamed SOG format specification pages (EN/JA) and linked them from the sidebar + formats index.
• Fixed SOG spec inaccuracies (log-domain scales codebook decoding, quaternion ordering/mode mapping, antialias optionality, plus missing asset in JA).
• Renamed “LOD streaming” → “Streamed SOG” across relevant guides/tutorials while preserving existing URLs/anchors.

Reviewed changes

Copilot reviewed 27 out of 27 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sidebars.js	Adds the new Streamed SOG format page to the Gaussian splatting formats sidebar group.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/web-components/tags/pc-splat.md	Updates pc-splat tag docs terminology to “Streamed SOG”.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/supersplat/upload.md	Renames SSOG upload option label/description to Streamed SOG terminology.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/supersplat/streaming.md	Updates SuperSplat streaming page wording to Streamed SOG terminology.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/supersplat/index.md	Updates SuperSplat overview copy to Streamed SOG terminology.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/splat-transform/index.md	Updates Streamed SOG generation section naming and references.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/rendering-architecture/splat-data-format.md	Replaces “LOD streaming resources” wording with “Streamed SOG resources”.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/rendering-architecture/index.md	Updates rendering architecture page references from LOD streaming to Streamed SOG.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/formats/streamed-sog.md	Adds Japanese Streamed SOG format specification (new doc page).
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/formats/sog.md	Applies SOG spec fixes (asset metadata, optional antialias, log-domain scales, quaternion order/mode).
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/formats/index.md	Expands formats index to include Streamed SOG + comparison table/workflow updates.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/building/performance.md	Updates performance guide sections/phrasing to Streamed SOG terminology.
i18n/ja/docusaurus-plugin-content-docs/current/user-manual/gaussian-splatting/building/lod-streaming.md	Retitles/rewrites the “LOD streaming” guide content to “Streamed SOG” while keeping the slug.
i18n/ja/docusaurus-plugin-content-docs/current/tutorials/gaussian-splat-streaming-lod.md	Updates tutorial title/description/intro to Streamed SOG terminology.
docs/user-manual/web-components/tags/pc-splat.md	Updates pc-splat tag docs terminology to “Streamed SOG”.
docs/user-manual/supersplat/upload.md	Renames SSOG upload option label/description to Streamed SOG terminology.
docs/user-manual/supersplat/streaming.md	Updates SuperSplat streaming page wording to Streamed SOG terminology.
docs/user-manual/supersplat/index.md	Updates SuperSplat overview copy to Streamed SOG terminology.
docs/user-manual/splat-transform/index.md	Updates Streamed SOG generation section naming and references.
docs/user-manual/gaussian-splatting/rendering-architecture/splat-data-format.md	Replaces “LOD streaming resources” wording with “Streamed SOG resources”.
docs/user-manual/gaussian-splatting/rendering-architecture/index.md	Updates rendering architecture page references from LOD streaming to Streamed SOG.
docs/user-manual/gaussian-splatting/formats/streamed-sog.md	Adds English Streamed SOG format specification (new doc page).
docs/user-manual/gaussian-splatting/formats/sog.md	Applies SOG spec fixes (optional antialias, log-domain scales, quaternion order/mode).
docs/user-manual/gaussian-splatting/formats/index.md	Expands formats index to include Streamed SOG + comparison table/workflow updates.
docs/user-manual/gaussian-splatting/building/performance.md	Updates performance guide sections/phrasing to Streamed SOG terminology.
docs/user-manual/gaussian-splatting/building/lod-streaming.md	Retitles/rewrites the “LOD streaming” guide content to “Streamed SOG” while keeping the slug.
docs/tutorials/gaussian-splat-streaming-lod.md	Updates tutorial title/description/intro to Streamed SOG terminology.

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[Copilot]

Pull request overview

Copilot reviewed 31 out of 31 changed files in this pull request and generated 2 comments.