WIP: Refactor agent package - not compiling

- Renamed AppMessage to AgentMessage throughout
- New agent-loop.ts with AgentLoopContext, AgentLoopConfig
- Removed transport abstraction, Agent now takes streamFn directly
- Extracted streamProxy to proxy.ts utility
- Removed agent-loop from pi-ai (now in agent package)
- Updated consumers (coding-agent, mom) for AgentMessage rename
- Tests updated but some consumers still need migration

Known issues:
- AgentTool, AgentToolResult not exported from pi-ai
- Attachment not exported from pi-agent-core
- ProviderTransport removed but still referenced
- messageTransformer -> convertToLlm migration incomplete
- CustomMessages declaration merging not working properly

packages/agent/test/utils/get-current-time.ts

@@ -0,0 +1,46 @@
+import { type Static, Type } from "@sinclair/typebox";
+import type { AgentTool, AgentToolResult } from "../../src/types.js";
+
+export interface GetCurrentTimeResult extends AgentToolResult<{ utcTimestamp: number }> {}
+
+export async function getCurrentTime(timezone?: string): Promise<GetCurrentTimeResult> {
+	const date = new Date();
+	if (timezone) {
+		try {
+			const timeStr = date.toLocaleString("en-US", {
+				timeZone: timezone,
+				dateStyle: "full",
+				timeStyle: "long",
+			});
+			return {
+				content: [{ type: "text", text: timeStr }],
+				details: { utcTimestamp: date.getTime() },
+			};
+		} catch (_e) {
+			throw new Error(`Invalid timezone: ${timezone}. Current UTC time: ${date.toISOString()}`);
+		}
+	}
+	const timeStr = date.toLocaleString("en-US", { dateStyle: "full", timeStyle: "long" });
+	return {
+		content: [{ type: "text", text: timeStr }],
+		details: { utcTimestamp: date.getTime() },
+	};
+}
+
+const getCurrentTimeSchema = Type.Object({
+	timezone: Type.Optional(
+		Type.String({ description: "Optional timezone (e.g., 'America/New_York', 'Europe/London')" }),
+	),
+});
+
+type GetCurrentTimeParams = Static<typeof getCurrentTimeSchema>;
+
+export const getCurrentTimeTool: AgentTool<typeof getCurrentTimeSchema, { utcTimestamp: number }> = {
+	label: "Current Time",
+	name: "get_current_time",
+	description: "Get the current date and time",
+	parameters: getCurrentTimeSchema,
+	execute: async (_toolCallId: string, args: GetCurrentTimeParams) => {
+		return getCurrentTime(args.timezone);
+	},
+};