feat(i18n): Add Internationalization Support for UI and LLM Output (#1058)

docs/cli/commands.md

@@ -195,6 +195,16 @@ Slash commands provide meta-level control over the CLI itself.
 - **`/init`**
   - **Description:** Analyzes the current directory and creates a `QWEN.md` context file by default (or the filename specified by `contextFileName`). If a non-empty file already exists, no changes are made. The command seeds an empty file and prompts the model to populate it with project-specific instructions.
 
+- [**`/language`**](./language.md)
+  - **Description:** View or change the language setting for both UI and LLM output.
+  - **Sub-commands:**
+    - **`ui`**: Set the UI language (zh-CN or en-US)
+    - **`output`**: Set the LLM output language
+  - **Usage:** `/language [ui|output] [language]`
+  - **Examples:**
+    - `/language ui zh-CN` (set UI language to Simplified Chinese)
+    - `/language output English` (set LLM output language to English)
+
 ### Custom Commands
 
 For a quick start, see the [example](#example-a-pure-function-refactoring-command) below.

docs/cli/language.md

@@ -0,0 +1,71 @@
+# Language Command
+
+The `/language` command allows you to customize the language settings for both the Qwen Code user interface (UI) and the language model's output. This command supports two distinct functionalities:
+
+1. Setting the UI language for the Qwen Code interface
+2. Setting the output language for the language model (LLM)
+
+## UI Language Settings
+
+To change the UI language of Qwen Code, use the `ui` subcommand:
+
+```
+/language ui [zh-CN|en-US]
+```
+
+### Available UI Languages
+
+- **zh-CN**: Simplified Chinese (简体中文)
+- **en-US**: English
+
+### Examples
+
+```
+/language ui zh-CN    # Set UI language to Simplified Chinese
+/language ui en-US    # Set UI language to English
+```
+
+### UI Language Subcommands
+
+You can also use direct subcommands for convenience:
+
+- `/language ui zh-CN` or `/language ui zh` or `/language ui 中文`
+- `/language ui en-US` or `/language ui en` or `/language ui english`
+
+## LLM Output Language Settings
+
+To set the language for the language model's responses, use the `output` subcommand:
+
+```
+/language output <language>
+```
+
+This command generates a language rule file that instructs the LLM to respond in the specified language. The rule file is saved to `~/.qwen/output-language.md`.
+
+### Examples
+
+```
+/language output 中文      # Set LLM output language to Chinese
+/language output English   # Set LLM output language to English
+/language output 日本語    # Set LLM output language to Japanese
+```
+
+## Viewing Current Settings
+
+When used without arguments, the `/language` command displays the current language settings:
+
+```
+/language
+```
+
+This will show:
+
+- Current UI language
+- Current LLM output language (if set)
+- Available subcommands
+
+## Notes
+
+- UI language changes take effect immediately and reload all command descriptions
+- LLM output language settings are persisted in a rule file that is automatically included in the model's context
+- To request additional UI language packs, please open an issue on GitHub