[FEATURE] VS Code extension: Explorer and Source Control follow the active session's folder

Problem Statement

I run Claude Code sessions in several repos at once from one VS Code window. One session runs in the Claude panel on the folder the window has open. Others I start with claude in integrated terminals, each in a sibling repo. Each session works in its own directory, but Explorer and Source Control stay on the window's folder. When I switch to a session working in another repo, I can't see the files it's editing or the changes it has made. To see them I have to open that folder by hand or open a second window.

Proposed Solution

Make Explorer and Source Control follow the active session. When I switch to a session whose working directory is outside the window's folder, those views switch to that directory. This applies whether the session is a panel tab or a terminal running claude. Switching back to a session in the window's folder brings the original views back.

Alternative Solutions

• One VS Code window per repo. This works, but it costs screen space and window switching, and I can't see the sessions side by side.
• A multi-root workspace. The extension always uses the first folder, and there's no way to choose another (#58044, closed as not planned after going inactive).

Use Case Example

The window is open on repo A, and a panel session works in A. A terminal session works in sibling repo B, fixing findings from code review. When I switch to the B session, I want Explorer to show B and Source Control to show B's changes, so I can read the diff before the session pushes.

Additional Context

Related: #58044.