fix(webgl): the browser menu before the game data — no ghost images, singleplayer waits for the data, compressed download (#2185 #2186 #2187)

[marceld23]

Closes #2185
Closes #2186
Closes #2187

What happened

On the first visit after the v2026.10.2 update (/play), the auto-opened "What's new?" stayed on screen after it was closed. Menu, loading screen and the "New world?" dialog were drawn on top of each other, the background was black and the logo smeared. "New world" → "Delete and start over" did nothing for a long time, then ended in "The world could not be started in this browser". A reload made it work.

One root cause. The browser menu is up before the game data has downloaded and parsed. The data cache is stamped with the version, so every release re-downloads it: 56 files, ~20 MB of JSON, served uncompressed (measured live; settlement_templates.json 6.8 MB → 194 KB gzipped). During that window:

• Browser: shell screens leave ghost images before the game data has loaded — no camera clears the screen #2185: nothing cleared the screen. Launcher.unity has no camera, and the backdrop's camera (MenuBackground) waits for the content. So every overlay canvas left ghost images.
• Browser singleplayer / New world started before the game data has loaded fails with "could not be started in this browser" #2186: BootBrowserSingleplayer started the in-process server with Content == null, and the GameServer constructor threw (ui.sp.browser_failed). The loading screen sat at 0 % meanwhile.
• C:/Program Files/Git/play serves 20 MB of game data uncompressed — enable Caddy compression on the WorldHost site #2187: 20 MB uncompressed per release made the window long.

Changes

• ShellClearCamera (new): created in AppShell.Awake; solid black, culling mask 0, depth -100. It enables itself in LateUpdate only while no other enabled camera renders to the screen; cameras with a target texture (preview rigs) do not count. The backdrop, the intro, the editors and the world rig take over as before.
• AppShell.BootBrowserSingleplayer: waits behind the loading screen until ContentReady. It stops if the phase changes, and returns to the menu (content-error overlay with Retry) if the download fails.
• UiLoading: while the browser data is still loading, the title reads "Loading game data… n/56" and the bar follows the download. New StreamingAssetsCache.RemoteFileTotal.
• Locale key ui.loading.data: all 14 languages, translated by hand.
• deploy/worldhost/docker-compose.yml: caddy.encode: zstd gzip. Caddy's default type list skips the Unity build files: they are Brotli-packed *.unityweb and go out as application/octet-stream (checked live).
• Docs: docs/developer/WEBCLIENT_FEASIBILITY.md §"The menu before the game data"; TODO.md entry.

Verification

• Locale guard test set (scripts/locale-test-filter.py): 395 passed, 0 failed.
• Local Unity build (scripts/build-client.ps1, Windows player): Build Finished, Result: Success; no generated files to commit.
• Unity EditMode (run-tests.ps1 -Suites UnityEdit): 176 total, 173 passed, 1 skipped. The new ShellClearCameraEditModeTests pass 7/7. The 2 failures are the known ones already on main: InputAbstractionEditModeTests.EveryAction_HasALabelKey_AndIsListedInARebindGroup (FeedCreature, since feat(creatures): begging herds — herds of 6–12, animals that beg for the food in your hand, a Feed action (Q); real giant sounds + a sand-sea VEGA line (#2018) #2023) and the stale ChunkMesherGoldenEditModeTests golden.
• ui.loading.data is hand-translated in all 14 locales; tools/locale_report.py shows 5268/5268 keys and clean for every language.

Rollout

• A + B (Browser: shell screens leave ghost images before the game data has loaded — no camera clears the screen #2185, Browser singleplayer / New world started before the game data has loaded fails with "could not be started in this browser" #2186) ship with the next client release (WebGL).
• C (C:/Program Files/Git/play serves 20 MB of game data uncompressed — enable Caddy compression on the WorldHost site #2187) takes effect with the next worldhost deploy (deploy.yml). After that deploy, check curl -s -o /dev/null -D - -H 'Accept-Encoding: gzip' …/play/StreamingAssets/data/settlement_templates.json (expects Content-Encoding), the same on …/play/Build/player-webgl.data.unityweb (expects none), and one browser load.

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