fix(copilotcli): update elicitation handler in copilot cli to use ask tool

[DonJayamanne]

Fixes #307962

[Copilot]

Pull request overview

Updates the Copilot CLI session/MCP integration so the MCP gateway can be started with a session-associated URI (instead of an always-random URI), aligning MCP tool-call context with the originating chat session.

Changes:

• Extend ICopilotCLIMCPHandler.loadMcpConfig to accept a sessionUri and forward it to IMcpService.startMcpGateway.
• Update CopilotCLISessionService to pass a session-derived URI into MCP config loading for both session creation and session resume.
• Adjust CLI test helpers to match the updated MCP handler interface.

Show a summary per file

File	Description
extensions/copilot/src/extension/chatSessions/copilotcli/node/test/testHelpers.ts	Updates the null MCP handler stub to accept a resource/URI parameter.
extensions/copilot/src/extension/chatSessions/copilotcli/node/mcpHandler.ts	Threads a session URI through MCP config loading and into startMcpGateway.
extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts	Provides a session-derived URI to loadMcpConfig when creating/resuming CLI sessions.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 1

[Copilot]

When options.sessionId is not provided, the gateway resource falls back to a random copilot-cli URI. That resource does not match the chat session resource shape used elsewhere (SessionIdForCLI.getResource(...) → scheme copilotcli), so MCP gateway tool calls won’t be associated with the actual chat session (and inline elicitation/ask UX will still differ in these code paths, e.g. delegation / untitled sessions). Consider ensuring a session id/resource is always available before starting the gateway (e.g. generate a sessionId up-front when missing, use SessionIdForCLI.getResource(sessionId) for the gateway resource, and pass the same sessionId through to sessionManager.createSession).

See below for a potential fix:

		const sessionId = options.sessionId ?? generateUuid();
		const resource = SessionIdForCLI.getResource(sessionId);
		const { mcpConfig: mcpServers, disposable: mcpGateway } = await this.mcpHandler.loadMcpConfig(resource);
		try {
			const sessionOptions = await this.createSessionsOptions({ ...options, sessionId, mcpServers });
			const sessionManager = await raceCancellationError(this.getSessionManager(), token);
			const sdkSession = await sessionManager.createSession({ ...sessionOptions, sessionId });