* [AI Chat] Progress indicator with text and expansion button
Introduce ProgressBubble UI component.
Replaces spinner during generation and tool use, adding text description of the operation currently in progress.
Replaces AssistantTask tabs ("Steps"/"Progress") with a button to control expansion and collapse of details.
Replaces SearchSummary special handling with status inside the ProgressBubble and a regular search Tool Use event rendering when detail is expanded.
Pete Miller
593f937bfa