0.2.5-dev: merge claude/036-scene

# Conflicts:
#	CHANGELOG.md
#	docs/history/0.2.5.md

docs/history/0.2.5.md

@@ -366,3 +366,51 @@ replace 设置 → 问题反馈.
 Tests: `test/sim/official-damage-numbers.test.js`, `test/ui/official-damage-numbers.test.js`,
 `test/render/official-numbers.test.js`. Golden digests do not move: no new event kind is emitted, and the extra
 tuple field is not part of the digest. Player notes: PLAYING; client notes: design/client.md.
+
+### 30.17 Official battlefield scenes (#532)
+
+Report: the web board draws the metal theme for every battlefield. The reporter asked for the sand theme.
+PR #533 by @andrew05060414.
+
+Findings (2026-10-11; the official hot-update lists and asset indexes, read from the CDN, and the scene bundles of
+version `26-04-13-12-31-42_e9b560`):
+
+- The official board is not assembled at run time. Every battlefield is a prebuilt scene bundle, shipped only while
+  the season runs. DESIGN §15 said otherwise from an off-season list and is corrected there.
+- Which art a battlefield uses is the dependency list of its scene bundle: the sand theme for act1 m01–m07 and act2
+  m02 / m04, `map_lakegarden` + `map_syracuse_metro` for act2 m01, `map_kxmr` + `map_lm_center` for act2 m03. The
+  same in the 上半 version of 2025-11 and the 下半 versions of 2026-03 / 04. No battlefield uses the metal theme.
+- The sand theme bundle holds no mesh because the models are baked into each scene ("Combined Mesh (root: scene)").
+- A scene's three sub-graphics `HIDDEN@1…3` are the left normal field, the right normal field and the boss field.
+- `python3 tools/local-extract/fetch_scenes.py --list` against that Android hot-update list names 33 bundles and
+  22,801,308 bytes. That is the compressed CDN download, not the extracted size in the full zip.
+
+Change: `tools/local-extract/scenes.py` exports a battlefield's scene (meshes in board space, materials, key light,
+lightmap pages with the baked shadow mask in alpha, albedo textures) to `public/assets/local/scene/<stageId>/`;
+`extract.py --only scene` runs it, reading the scene bundles from the client, `--scenes <dir>` or
+`.cache/official-scenes/*`; `tools/local-extract/fetch_scenes.py` downloads the in-season bundles from the official
+CDN (md5-checked against that version's hot-update list). The 3D board draws a stage's scene when the local-art
+manifest lists it (`board3d/load.js loadScenePack`, `scene.js setScenePack`); the procedural metal board stays the
+fallback and still draws the devices, gates, field edges and terrain overlays.
+
+Owner decision (2026-10-12): the eleven scenes belong to the 0.2.5 asset pack. The maintainer's full release zip
+includes the extracted files. A lite package or a source install may download and extract them on that machine
+(`node tools/setup.mjs --scenes`; `--no-scenes` skips). Missing Python 3.8+ or UnityPy / lz4 / Pillow is a warning,
+and the metal board remains. The repository never stores the bundles or the extracted files (`.gitignore` already
+ignores `public/assets/`, `data/local-assets.json` and `.cache/`, and names `.cache/official-scenes/`). Packaging
+does not fail when the scenes are absent; the summary line `battlefield scenes` says whether this machine has them.
+`scenes.py` and `fetch_scenes.py` ship in a player zip only after they are committed, because the packager reads
+`git ls-files`.
+
+No gameplay change: the scene is art under the same grid, camera and unit layer. Golden results are not moved by
+this change.
+
+**[ASSUMED]** the light gains `SCENE_LIGHT` (`range` 8.0, `ambient` 0.2, `direct` 0.8, `indirect` 0.4) and the RGBM
+reading of the lightmap pages (Unity linear decode, range 5), both in DESIGN §15. Not done: the scene's normal /
+metallic / emission maps, map effects, sky box and post-processing; the tile graphics a level switches at run time
+(mire, tide) still use the remake's overlays. The extracted byte size inside a full zip was not measured here.
+
+Tests: `test/render/board3d-scene.test.js` (the scene table against data/stages.json, board-space conversion, chunk
+layout shared by scenes.py and load.js, sub-graphic groups, RGBM decode, the loader with a fake store, BoardScene
+with a stub renderer: scene on / areas / fallback). `test/scene-assets.test.js` (setup's scene step, the full plan
+ships extracted scene files, the lite plan ships none, git ignores the bundles).