Improve tool execution rendering and error handling

- Show tool execution components immediately when tool calls appear in streaming
- Update components with streaming arguments as they come in
- Handle incomplete/partial arguments gracefully with optional chaining
- Fix error handling: tools now throw exceptions instead of returning error messages
- Fix bash abort handling to properly reject on abort/timeout
- Clean up error display

packages/coding-agent/src/tui/user-message.ts

@@ -4,7 +4,6 @@ import { Container, Markdown, Spacer } from "@mariozechner/pi-tui";
  * Component that renders a user message
  */
 export class UserMessageComponent extends Container {
-	private spacer: Spacer | null = null;
 	private markdown: Markdown;
 
 	constructor(text: string, isFirst: boolean) {
@@ -12,8 +11,7 @@ export class UserMessageComponent extends Container {
 
 		// Add spacer before user message (except first one)
 		if (!isFirst) {
-			this.spacer = new Spacer(1);
-			this.addChild(this.spacer);
+			this.addChild(new Spacer(1));
 		}
 
 		// User messages with dark gray background