Add issue reporting for failed chat session loads in Copilot CLI

[DonJayamanne]

No description provided.

[Copilot]

Pull request overview

Adds a more actionable warning for Copilot CLI chat sessions that fail to load by including a pre-filled “report an issue” link with environment details, and updates the unit test vscode mock to support the new runtime info gathering.

Changes:

• Generate runtime/environment info (platform, VS Code version, extension version) for session-load failure reporting.
• Replace the plain invalid-session warning with a Markdown warning containing a “report an issue” link.
• Extend the Vitest vscode mock to include env, version, and extensions.getExtension().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/extension/chatSessions/vscode-node/copilotCLIChatSessionsContribution.ts	Builds a GitHub issue URL/body for session-load failures and surfaces it via a Markdown warning link.
src/extension/chatSessions/vscode-node/test/copilotCLIChatSessionParticipant.spec.ts	Updates the mocked vscode module to provide the new env/version/extensions fields used by the contribution code.