feat(other-models): announce the feature only when folders are available

Other Models management is opt-in and its folders come from
folder_paths.get_folder_paths(). In plugin mode ComfyUI registers vae,
upscale_models, text_encoders, clip_vision and controlnet out of the box, so
enabling the feature works immediately. Standalone only knows the keys present
in settings.json.folder_paths, and that file is edited by hand - there is no UI
for those keys - so a standalone user who followed the announcement banner
reached "Enable Other Models" and then an empty page.

Gate the announcement on the capability instead of on how the process was
started:

- Config.get_other_models_availability() probes every canonical other key
  (legacy clip collapses into text_encoders where the host exposes
  map_legacy) and reports which sub_types resolve to a folder that exists on
  disk. It deliberately ignores enable_other_models: the question is "could
  this work here at all?". An empty folder counts, because CivitAI downloads
  can target it.
- /api/lm/settings exposes it as the derived, non-persisted
  other_models_paths_available flag; a probe failure yields null and the
  banner fails open.
- BannerService only registers the announcement when the flag is not false.
  `=== false` (not falsy) keeps a cached/older payload working, and nothing is
  written to dismissed_banners, so the banner can return once folders exist.
- The Other page grows an "enabled but nothing to scan" empty state driven by
  config.other_roots, showing the settings.json snippet for standalone and a
  pointer to ComfyUI model paths otherwise, plus an Open Settings action. It
  also covers the corner where only a non-default sub_type has a folder.

Translate the six other.noPaths.* keys into all nine locales and record the
new "folder key" / "on disk" terminology in the i18n guidelines.

Backend tests and pytest tests/i18n could not run in this environment (no
pytest/platformdirs); the probe was exercised against a stubbed folder_paths.
Frontend: 120 files / 1101 JS tests passed.

docs/i18n-translation-guidelines.md

@@ -27,6 +27,12 @@ Locales: `en`, `zh-CN`, `zh-TW`, `ja`, `ko`, `fr`, `de`, `es`, `ru`, `he` (RTL).
 > default set — keep all three enumerating the full five (`VAE / upscaler / text encoder /
 > CLIP vision / ControlNet` in `en`; locale slash-list casing follows each file's existing
 > `VAE / Upscaler / Text Encoder / …` style, de compounds as `CLIP-Vision- und ControlNet-Ordner`).
+>
+> **Status (2026-09, "no folders found" state):** the Other Models page gained an *enabled but
+> nothing to scan* empty state with 6 new keys (`other.noPaths.*`); translated in all 9 locales
+> in the same pass. The `folder_paths` JSON snippet shown in that state lives in
+> `templates/other.html`, **not** in the locale files, so it is never translated — only the
+> surrounding prose is. Terminology added in §2.
 
 ---
 
@@ -273,6 +279,19 @@ In prose these names sit next to localized nouns the same way `Diffusion Model`
 each locale's `header.filter.modelTypes` rendering (zh `管理的模型类型`, ja `管理するモデルタイプ`,
 de `Verwaltete Modelltypen`, …).
 
+The "no folders found" empty state (`other.noPaths.*`) uses two phrases that must stay
+consistent whenever that copy is edited. `folder key` means the `folder_paths` key name
+(`vae`, `upscale_models`, … — Latin per the table above); `on disk` means the folder must
+physically exist:
+
+| Phrase | Rendering |
+|---|---|
+| folder key | zh-CN 文件夹键 · zh-TW 資料夾鍵 · ja フォルダーキー · ko 폴더 키 · fr clé de dossier · de Ordnerschlüssel · es clave de carpeta · ru ключ папки · he מפתח תיקייה |
+| on disk | zh-CN 在磁盘上 · zh-TW 在磁碟上 · ja ディスク上 · ko 디스크에 · fr sur le disque · de auf dem Datenträger · es en el disco · ru на диске · he בדיסק |
+
+`settings.json` and `ComfyUI` stay verbatim in every locale; "reload this page" / "restart
+LoRA Manager" reuse each locale's existing restart wording (`settings.extraFolderPaths.*`).
+
 ---
 
 ## 3. Cross-cutting confusion hot-spots (must-fix list)