Try to clean up inProgress handling for chat sessions

[mjbvz]

This api is very strange. Reducing where it's exposed because it really should not exist

[Copilot]

Pull request overview

This PR refactors “in progress” tracking for chat/agent sessions by removing the externally-callable reporting API and switching consumers to work with chatSessionType identifiers instead of precomputed display names, with the goal of reducing exposure of a brittle API surface.

Changes:

• Removed reportInProgress(...) from IChatSessionsService and adjusted getInProgress() to return { chatSessionType, count }.
• Updated the chat status dashboard to resolve a display name from chatSessionType (with special-cases for built-in agent providers).
• Adjusted mocks and internal tracking maps to key by chatSessionType rather than display name.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/vs/workbench/contrib/chat/test/common/mockChatSessionsService.ts	Updates mock getInProgress() shape to return chatSessionType keys.
src/vs/workbench/contrib/chat/common/chatSessionsService.ts	Removes reportInProgress from the service interface and deprecates getInProgress().
src/vs/workbench/contrib/chat/browser/chatStatus/chatStatusDashboard.ts	Updates UI rendering to map chatSessionType → display label before showing “in progress” rows.
src/vs/workbench/contrib/chat/browser/chatSessions/chatSessions.contribution.ts	Internal refactor of in-progress bookkeeping to store counts by chatSessionType and update counts on item deltas.