chore(agent): rename package references from pi-agent to pi-agent-core (#1149)

Update all documentation and changelog references to use the new
package name @mariozechner/pi-agent-core.

https://claude.ai/code/session_019KyWMa1gGypeHxM4N3eu44

Co-authored-by: Claude <noreply@anthropic.com>

packages/agent/CHANGELOG.md

@@ -167,7 +167,7 @@
 
 - **`UserMessageWithAttachments` and `Attachment` types removed**: Attachment handling is now the responsibility of the `convertToLlm` function.
 
-- **Agent loop moved from `@mariozechner/pi-ai`**: The `agentLoop`, `agentLoopContinue`, and related types have moved to this package. Import from `@mariozechner/pi-agent` instead.
+- **Agent loop moved from `@mariozechner/pi-ai`**: The `agentLoop`, `agentLoopContinue`, and related types have moved to this package. Import from `@mariozechner/pi-agent-core` instead.
 
 ### Added
 

packages/agent/README.md

@@ -1,17 +1,17 @@
-# @mariozechner/pi-agent
+# @mariozechner/pi-agent-core
 
 Stateful agent with tool execution and event streaming. Built on `@mariozechner/pi-ai`.
 
 ## Installation
 
 ```bash
-npm install @mariozechner/pi-agent
+npm install @mariozechner/pi-agent-core
 ```
 
 ## Quick Start
 
 ```typescript
-import { Agent } from "@mariozechner/pi-agent";
+import { Agent } from "@mariozechner/pi-agent-core";
 import { getModel } from "@mariozechner/pi-ai";
 
 const agent = new Agent({
@@ -293,7 +293,7 @@ Follow-up messages are checked only when there are no more tool calls and no ste
 Extend `AgentMessage` via declaration merging:
 
 ```typescript
-declare module "@mariozechner/pi-agent" {
+declare module "@mariozechner/pi-agent-core" {
   interface CustomAgentMessages {
     notification: { role: "notification"; text: string; timestamp: number };
   }
@@ -365,7 +365,7 @@ Thrown errors are caught by the agent and reported to the LLM as tool errors wit
 For browser apps that proxy through a backend:
 
 ```typescript
-import { Agent, streamProxy } from "@mariozechner/pi-agent";
+import { Agent, streamProxy } from "@mariozechner/pi-agent-core";
 
 const agent = new Agent({
   streamFn: (model, context, options) =>
@@ -382,7 +382,7 @@ const agent = new Agent({
 For direct control without the Agent class:
 
 ```typescript
-import { agentLoop, agentLoopContinue } from "@mariozechner/pi-agent";
+import { agentLoop, agentLoopContinue } from "@mariozechner/pi-agent-core";
 
 const context: AgentContext = {
   systemPrompt: "You are helpful.",