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/ai/src/index.ts

@@ -1,4 +1,3 @@
-export * from "./agent/index.js";
 export * from "./models.js";
 export * from "./providers/anthropic.js";
 export * from "./providers/google.js";
@@ -7,6 +6,7 @@ export * from "./providers/openai-completions.js";
 export * from "./providers/openai-responses.js";
 export * from "./stream.js";
 export * from "./types.js";
+export * from "./utils/event-stream.js";
 export * from "./utils/oauth/index.js";
 export * from "./utils/overflow.js";
 export * from "./utils/typebox-helpers.js";