Improve web-ui message and tool UX

- Add collapsible thinking blocks with shimmer animation during streaming
- Update user messages to use orange gradient pill styling (matching sitegeist)
- Fix cost display to only show for completed messages, not while streaming
- Update tool renderers to use ChevronsUpDown/ChevronUp icons instead of rotating ChevronRight
- Export ThinkingBlock component from public API

packages/web-ui/src/components/MessageList.ts

@@ -65,7 +65,7 @@ export class MessageList extends LitElement {
 					template: html`<assistant-message
 						.message=${amsg}
 						.tools=${this.tools}
-						.isStreaming=${this.isStreaming}
+						.isStreaming=${false}
 						.pendingToolCalls=${this.pendingToolCalls}
 						.toolResultsById=${resultByCallId}
 						.hideToolCalls=${false}