[BUG] macOS dictation (voice input) is misrecognized as English in the chat input, even when macOS dictation language is set to Japanese only

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

## Environment
- Claude Code VSCode extension version: 2.1.273 (darwin-arm64)
- OS: macOS (Darwin 25.6.0)
- Editor: VSCode
- macOS Dictation language setting: Japanese only (English not registered)

## Description
When using macOS dictation (voice input) inside the Claude Code chat input panel, spoken Japanese is transcribed as English text, even though:
- System Settings → Keyboard → Dictation → Language is set to Japanese only (no other languages registered)
- No relevant voice/dictation/language setting exists in the Claude Code extension's contributed settings (`claudeCode.*` in package.json)

## Steps to Reproduce
1. Set macOS Dictation language to Japanese only in System Settings.
2. Open the Claude Code chat panel in VSCode.
3. Place the cursor in the chat input box.
4. Start dictation (e.g., double-tap Fn) and speak in Japanese.
5. Observe the transcribed text appears in English instead of Japanese.

## Isolation / Comparison
- Performing the exact same dictation test with the cursor placed in a normal VSCode text editor (a Markdown file) correctly transcribes as Japanese.
- The issue only occurs when the cursor is inside the Claude Code chat input webview, suggesting the input field may be missing a `lang="ja"` attribute (or similar), or has some `inputmode`/`autocomplete` configuration that causes macOS dictation to default to English in that specific context.

## Expected Behavior
Dictation inside the Claude Code chat input should respect the macOS system dictation language setting (Japanese), consistent with behavior in the standard VSCode editor.

## Actual Behavior
Dictation inside the Claude Code chat input is transcribed in English regardless of the macOS dictation language setting.

### What Should Happen?

## Environment
- Claude Code VSCode extension version: 2.1.273 (darwin-arm64)
- OS: macOS (Darwin 25.6.0)
- Editor: VSCode
- macOS Dictation language setting: Japanese only (English not registered)

## Description
When using macOS dictation (voice input) inside the Claude Code chat input panel, spoken Japanese is transcribed as English text, even though:
- System Settings → Keyboard → Dictation → Language is set to Japanese only (no other languages registered)
- No relevant voice/dictation/language setting exists in the Claude Code extension's contributed settings (`claudeCode.*` in package.json)

## Steps to Reproduce
1. Set macOS Dictation language to Japanese only in System Settings.
2. Open the Claude Code chat panel in VSCode.
3. Place the cursor in the chat input box.
4. Start dictation (e.g., double-tap Fn) and speak in Japanese.
5. Observe the transcribed text appears in English instead of Japanese.

## Isolation / Comparison
- Performing the exact same dictation test with the cursor placed in a normal VSCode text editor (a Markdown file) correctly transcribes as Japanese.
- The issue only occurs when the cursor is inside the Claude Code chat input webview, suggesting the input field may be missing a `lang="ja"` attribute (or similar), or has some `inputmode`/`autocomplete` configuration that causes macOS dictation to default to English in that specific context.

## Expected Behavior
Dictation inside the Claude Code chat input should respect the macOS system dictation language setting (Japanese), consistent with behavior in the standard VSCode editor.

## Actual Behavior
Dictation inside the Claude Code chat input is transcribed in English regardless of the macOS dictation language setting.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

## Environment
- Claude Code VSCode extension version: 2.1.273 (darwin-arm64)
- OS: macOS (Darwin 25.6.0)
- Editor: VSCode
- macOS Dictation language setting: Japanese only (English not registered)

## Description
When using macOS dictation (voice input) inside the Claude Code chat input panel, spoken Japanese is transcribed as English text, even though:
- System Settings → Keyboard → Dictation → Language is set to Japanese only (no other languages registered)
- No relevant voice/dictation/language setting exists in the Claude Code extension's contributed settings (`claudeCode.*` in package.json)

## Steps to Reproduce
1. Set macOS Dictation language to Japanese only in System Settings.
2. Open the Claude Code chat panel in VSCode.
3. Place the cursor in the chat input box.
4. Start dictation (e.g., double-tap Fn) and speak in Japanese.
5. Observe the transcribed text appears in English instead of Japanese.

## Isolation / Comparison
- Performing the exact same dictation test with the cursor placed in a normal VSCode text editor (a Markdown file) correctly transcribes as Japanese.
- The issue only occurs when the cursor is inside the Claude Code chat input webview, suggesting the input field may be missing a `lang="ja"` attribute (or similar), or has some `inputmode`/`autocomplete` configuration that causes macOS dictation to default to English in that specific context.

## Expected Behavior
Dictation inside the Claude Code chat input should respect the macOS system dictation language setting (Japanese), consistent with behavior in the standard VSCode editor.

## Actual Behavior
Dictation inside the Claude Code chat input is transcribed in English regardless of the macOS dictation language setting.

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

2.1.273

### Platform

Anthropic API

### Operating System

macOS

### Terminal/Shell

Terminal.app (macOS)

### Additional Information

_No response_

Reproduce the issue on macOS in the Claude Code chat input webview, then inspect the webview input and the contributed settings described in package.json. Compare its language, inputmode, and autocomplete configuration with a normal VSCode editor where Japanese dictation works. Done means Japanese macOS dictation is preserved in the chat input without affecting ordinary text entry.

Written by the indexing model from the issue text.