Add CHANGELOG.md to agent package with refactor details

packages/agent/CHANGELOG.md

@@ -0,0 +1,69 @@
+# Changelog
+
+## [Unreleased]
+
+### Breaking Changes
+
+- **Transport abstraction removed**: `ProviderTransport`, `AppTransport`, and `AgentTransport` interface have been removed. The `Agent` class now takes a `streamFn` option directly for custom streaming implementations.
+
+- **Agent options renamed**:
+  - `transport` → removed (use `streamFn` instead)
+  - `messageTransformer` → `convertToLlm` (converts `AgentMessage[]` to LLM-compatible `Message[]`)
+  - `preprocessor` → `transformContext` (transforms `AgentMessage[]` before `convertToLlm`)
+
+- **AppMessage renamed to AgentMessage**: All references to `AppMessage` have been renamed to `AgentMessage` for consistency.
+
+- **Agent loop moved from pi-ai**: The `agentLoop`, `agentLoopContinue`, and related types (`AgentContext`, `AgentEvent`, `AgentTool`, `AgentToolResult`, `AgentToolUpdateCallback`, `AgentLoopConfig`) have moved from `@mariozechner/pi-ai` to this package.
+
+### Added
+
+- **`streamFn` option**: Pass a custom stream function to the Agent for proxy backends or custom implementations. Default uses `streamSimple` from pi-ai.
+
+- **`streamProxy` utility**: New helper function for browser apps that need to proxy through a backend server. Replaces `AppTransport`.
+
+- **`getApiKey` option**: Dynamic API key resolution for expiring OAuth tokens (e.g., GitHub Copilot).
+
+- **`AgentLoopContext` and `AgentLoopConfig`**: Exported types for the low-level agent loop API.
+
+- **`agentLoop` and `agentLoopContinue`**: Low-level functions for running the agent loop directly without the `Agent` class wrapper.
+
+### Migration Guide
+
+**Before (0.30.x):**
+```typescript
+import { Agent, ProviderTransport } from '@mariozechner/pi-agent-core';
+
+const agent = new Agent({
+  transport: new ProviderTransport({ apiKey: '...' }),
+  messageTransformer: (messages) => messages.filter(...),
+  preprocessor: async (messages) => compactMessages(messages)
+});
+```
+
+**After:**
+```typescript
+import { Agent } from '@mariozechner/pi-agent-core';
+import { streamSimple } from '@mariozechner/pi-ai';
+
+const agent = new Agent({
+  streamFn: streamSimple,  // or omit for default
+  convertToLlm: (messages) => messages.filter(...),
+  transformContext: async (messages) => compactMessages(messages),
+  getApiKey: async (provider) => resolveApiKey(provider)
+});
+```
+
+**For proxy usage (replaces AppTransport):**
+```typescript
+import { Agent, streamProxy } from '@mariozechner/pi-agent-core';
+
+const agent = new Agent({
+  streamFn: (model, context, options) => streamProxy(
+    '/api/agent',
+    model,
+    context,
+    options,
+    { 'Authorization': 'Bearer ...' }
+  )
+});
+```