Add Hindi (`hi`) localization support, including custom-node `nodeDefs.json` files

### What problem are you experiencing?

I maintain [ComfyUI OpenPose Studio](https://github.com/andreszs/ComfyUI-OpenPose-Studio), which already ships a Hindi localization for its JavaScript modal UI and a corresponding [`locales/hi/nodeDefs.json`](https://github.com/andreszs/ComfyUI-OpenPose-Studio/blob/main/locales/hi/nodeDefs.json) for its ComfyUI nodes.

The modal UI can be displayed in Hindi because the extension handles those JavaScript strings itself. However, the node names, inputs, outputs, widgets, and descriptions remain in English because ComfyUI Frontend does not currently recognize `hi` as a supported locale.

As a result, custom-node authors can provide a valid Hindi `nodeDefs.json`, but ComfyUI ignores it. This creates an inconsistent, partially translated experience and prevents extensions from delivering complete Hindi localization through the official i18n mechanism.

### When does this problem occur?

This happens every time a user attempts to use ComfyUI in Hindi:

1. The custom node provides `locales/hi/nodeDefs.json`.
2. Its JavaScript UI can load the Hindi strings independently.
3. ComfyUI Frontend does not expose Hindi in the locale selector or resolve `hi` / `hi-IN` as a supported locale.
4. The extension's node definitions therefore remain in English.

This affects any custom node that wants to provide Hindi node translations, not only OpenPose Studio.

### How often do you encounter this problem?

Multiple times per day

### How much does this problem affect your workflow?

Significantly slows down my work

### Current workarounds

Custom nodes can implement their own localization system for JavaScript dialogs and other extension-owned interfaces, as OpenPose Studio currently does.

There is no equivalent clean workaround for node definitions. Users must keep the node names and controls in English, or modify/patch the frontend outside the supported localization workflow.

### Ideas for solutions (Optional)

Please add Hindi as an officially supported frontend locale:

- Register the `hi` locale and display it as `हिन्दी` in the locale selector.
- Resolve both `hi` and regional browser locales such as `hi-IN` to the Hindi locale.
- Add the standard frontend locale files for Hindi.
- Ensure that custom-node `locales/hi/nodeDefs.json` files are loaded and merged in the same way as files for the currently supported locales.
- Preserve the existing English fallback for untranslated strings.

The frontend's own [translation contribution guide](https://github.com/Comfy-Org/ComfyUI_frontend/blob/main/src/locales/CONTRIBUTING.md) already documents the process for adding new languages.

### Additional context

India had an estimated population of **1,463,866,000 in 2025**, according to [United Nations Data](https://data.un.org/en/iso/IN.html). India is linguistically diverse, but enabling Hindi would still make ComfyUI substantially more accessible to a very large potential user community.

OpenPose Studio already provides a complete [Hindi README and usage guide](https://github.com/andreszs/ComfyUI-OpenPose-Studio/blob/main/docs/README.hi.md), along with translated JavaScript modals and the currently unused Hindi node definitions.

### OpenPose Studio running in Hindi

[](https://github.com/andreszs/ComfyUI-OpenPose-Studio/blob/main/docs/README.hi.md)

_Click the screenshot to open the Hindi documentation._

### Node definitions still displayed in English

Despite the presence of the Hindi `nodeDefs.json`, the node and its controls remain untranslated:


Start with src/locales/CONTRIBUTING.md and compare the existing supported locale files and locale-selector setup. Check how locales/hi/nodeDefs.json is expected to be discovered and merged, including hi-IN resolution and English fallback. Done means Hindi is selectable, standard Hindi translations are present, and custom-node Hindi definitions load correctly.

Written by the indexing model from the issue text.