Adds the 18 `sceneTemplate.*` keys plus `fileMenu.newFromTemplate` to
all 15 locales. Until now the panel fell back to hardcoded Chinese, so
every non-Chinese user saw Chinese labels in an otherwise translated UI.
Simplified Chinese is taken verbatim from `scene_templates.toml` and
`TemplateScene::title_fallback()`, so the catalogue and the catalogue's
translation cannot drift apart while both exist.
The hardcoded fallbacks in `scene_template_panel` stay: they now only
fire when a key is missing, which is a backstop rather than the normal
path — and one that has already earned its place, since the panel
shipped ahead of these keys.
A dedicated integrity test asserts all 18 keys resolve in all 15
locales, on top of the existing cross-locale key-set equality.
The catalogue size moves 1273 -> 1291. The handoff for this work said
1263 -> 1281, computed against a stale baseline; taking that number
would have failed the integrity gate outright.
Co-authored-by: Codex <codex@openai.com>
Claude-Session: https://claude.ai/code/session_01FqKQqNj8exYwopGDpYUU7x
bf4a028ce9