Update VS Code proposed API definitions

[Copilot]

Syncs API definition files to latest versions from VS Code main branch via @vscode/dts.

Key API Changes

• ChatResponseExternalEditPart: New class for tracking edits from external tools
• ChatResponseStream.externalEdit(): Method to wrap external file modifications as agent edits
• ChatResponseMultiDiffPart: Added optional readOnly parameter to constructor
• ChatRequestModeInstructions: Added required name property
• Event properties: onDidPerformAction and onDidChangePauseState now readonly

Files Updated

• vscode.d.ts (+381 lines)
• vscode.proposed.chatParticipantAdditions.d.ts (+31 lines)
• vscode.proposed.chatParticipantPrivate.d.ts (+26 lines)
• vscode.proposed.languageModelThinkingPart.d.ts (+62 lines)

Extension compiles cleanly with updated definitions.

Original prompt

dsfsd

The user has attached the following uncommitted or modified files as relevant context:
Untitled-1
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Untitled-1
The user has attached the following file paths as relevant context:

• vscode.proposed.chatParticipantAdditions.d.ts

The user has attached the following files from their workspace:

• vscode.proposed.chatParticipantAdditions.d.ts

Created from VS Code via the GitHub Pull Request extension.

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