Update the chat panel title when the mode changes

[mjbvz]

Fixes #304274
cc @DonJayamanne

[Copilot]

Pull request overview

This PR aims to keep chat UI titles in sync when the underlying chat “mode”/session backing the widget changes, by ensuring host components react to view model/session transitions and refresh their title sources accordingly.

Changes:

• Update the chat view pane title control when the chat widget’s view model changes.
• Allow ChatEditorInput to switch which IChatModel it tracks (and rewire change listeners) after initial creation.
• Have the chat editor react to widget view model changes and update the associated ChatEditorInput to the new session model.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/widgetHosts/viewPane/chatViewPane.ts	Refreshes the view-pane title control when the widget swaps view models/sessions.
src/vs/workbench/contrib/chat/browser/widgetHosts/editor/chatEditorInput.ts	Adds support for retargeting the editor input to a new chat model and tracking its label/icon changes.
src/vs/workbench/contrib/chat/browser/widgetHosts/editor/chatEditor.ts	Listens for widget view model changes and updates the open editor input’s tracked model accordingly.

Copilot's findings

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