Sessions: Report cloud session pull requests

[benibenj]

Summary

• report provider-backed pull requests for Copilot Cloud sessions in the Agents window
• infer the pull request from cloud repository and branch metadata when the provider omits it
• share the Agent Host live PR polling, status icon, and persistent icon cache behavior

Testing

• Not run locally per request; validation is deferred to CI
• Pre-commit hygiene hook passed

[Copilot]

Pull request overview

Adds pull request reporting for Copilot Cloud sessions in the Agents window.

Changes:

• Resolves PRs from provider metadata or repository branch data.
• Shares live PR icon polling and caching behavior.
• Adds documentation and provider tests.

Show a summary per file

File	Description
copilotChatSessionsProvider.test.ts	Tests cloud PR resolution and icon updates.
COPILOT_CHAT_SESSIONS_PROVIDER.md	Documents cloud PR behavior.
copilotChatSessionsProvider.ts	Adds cloud PR inference and live icons.
baseAgentHostSessionsProvider.ts	Uses the shared icon helper.
pullRequestIconStatus.ts	Centralizes live and cached PR icon resolution.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 1
• Review effort level: Medium

[dmitrivMS]

@benibenj
Error: [core-ci ] [21:59:11] src/vs/sessions/contrib/providers/copilotChatSessions/browser/copilotChatSessionsProvider.ts(1066,3): error TS2322: Type 'IObservableWithChange<IGitHubInfo | { owner: string; repo: string; pullRequest: { number?: number | undefined; uri?: URI | undefined; baseRefOid?: string | undefined; headRefOid?: string | undefined; icon: ThemeIcon | undefined; }; } | undefined, unknown>' is not assignable to type 'IObservable<IGitHubInfo | undefined>'.