feat(coding-agent): expose deliverAs option in hook sendMessage() API

- pi.sendMessage(msg, options?) now accepts { triggerTurn?, deliverAs? }
- deliverAs: 'steer' (default) or 'followUp' controls delivery timing
- Update all mode handlers to pass options through
- Update file-trigger example to use new API
- Update CHANGELOG

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -404,10 +404,10 @@ export class InteractiveMode {
 
 		hookRunner.initialize({
 			getModel: () => this.session.model,
-			sendMessageHandler: (message, triggerTurn) => {
+			sendMessageHandler: (message, options) => {
 				const wasStreaming = this.session.isStreaming;
 				this.session
-					.sendHookMessage(message, { triggerTurn })
+					.sendHookMessage(message, options)
 					.then(() => {
 						// For non-streaming cases with display=true, update UI
 						// (streaming cases update via message_end event)