Display last used model info for Copilot CLI on chat panel

[anthonykim1]

Resolves: #303960

microsoft/vscode-copilot-chat#4605 didn't quite work for me — it returns ChatResult.details from the request handler, which is fine for local chat, but Copilot CLI goes through the chat session provider api, and on the first request the untitled session gets swapped out for a real one.

That swap makes VS Code throw away the in-memory chat model and rebuild history from scratch by replaying sdk events 🧐 — and the replay path was dropping result.details on the floor, so the model badge never made it back onto the first response.

After this PR you would see:

[github-actions]

Screenshot Changes

Base: 498c4699 Current: 52ad0c7e

Changed (2)

chat/aiCustomizations/aiCustomizationManagementEditor/McpBrowseMode/Light

Before	After

agentSessionsViewer/NeedsInput/Dark

Before	After

[Copilot]

Pull request overview

This PR ensures Copilot CLI sessions can display the “last used model” footer/badge reliably by preserving ChatResult.details through the contributed-session “untitled → real session” swap and subsequent history replay/rebuild paths.

Changes:

• Extend chat session history (and DTO/protocol plumbing) to carry optional details on response turns.
• Restore details onto the response model when VS Code rebuilds a contributed session from history.
• Teach Copilot CLI session reconstruction to attach model details to the final rebuilt response, and add/adjust tests.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/common/chatSessionsService.ts	Adds details?: string to response history items.
src/vs/workbench/contrib/chat/common/chatService/chatServiceImpl.ts	Applies replayed details onto the last request’s response result during session load.
src/vs/workbench/api/common/extHostChatSessions.ts	Serializes response-turn result.details into the session history DTO.
src/vs/workbench/api/common/extHost.protocol.ts	Extends IChatSessionHistoryItemDto (response) with details?: string.
src/vs/workbench/api/browser/mainThreadChatSessions.ts	Revives details from DTO into IChatSessionHistoryItem responses.
extensions/copilot/src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts	Returns a ChatResult.details string based on the selected CLI model (pre-swap).
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts	Computes model details during history rebuild and passes it into event→turn conversion.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotCli.ts	Introduces formatModelDetails() helper.
extensions/copilot/src/extension/chatSessions/vscode-node/test/copilotCLIChatSessionParticipant.spec.ts	Asserts handleRequest returns details for rendering as footer detail.
extensions/copilot/src/extension/chatSessions/copilotcli/common/copilotCLITools.ts	Allows injecting lastResponseDetails and applies it to the final rebuilt response turn.
extensions/copilot/src/extension/chatSessions/copilotcli/common/test/copilotCLITools.spec.ts	Adds coverage that rebuilt history preserves result.details.
extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotCliSessionService.spec.ts	Updates constructor call sites for the new ICopilotCLIModels dependency.

Copilot's findings

• Files reviewed: 12/12 changed files
• Comments generated: 1

[anthonykim1]

Could pass in result as in:

	export interface ChatResult {
		nextQuestion?: {
			prompt: string;
			participant?: string;
			command?: string;
		};
		/**
		 * An optional detail string that will be rendered at the end of the response in certain UI contexts.
		 */
		details?: string;
	}

but that seems like a waste since I doubt everything there would be something we would use in the future?