Add tool result streaming

- Add AgentToolUpdateCallback type and optional onUpdate callback to AgentTool.execute()
- Add tool_execution_update event with toolCallId, toolName, args, partialResult
- Normalize tool_execution_end to always use AgentToolResult (no more string fallback)
- Bash tool streams truncated rolling buffer output during execution
- ToolExecutionComponent shows last N lines when collapsed (not first N)
- Interactive mode handles tool_execution_update events
- Update RPC docs and ai/agent READMEs

fixes #44

packages/ai/src/agent/index.ts

@@ -1,3 +1,11 @@
 export { agentLoop, agentLoopContinue } from "./agent-loop.js";
 export * from "./tools/index.js";
-export type { AgentContext, AgentEvent, AgentLoopConfig, AgentTool, AgentToolResult, QueuedMessage } from "./types.js";
+export type {
+	AgentContext,
+	AgentEvent,
+	AgentLoopConfig,
+	AgentTool,
+	AgentToolResult,
+	AgentToolUpdateCallback,
+	QueuedMessage,
+} from "./types.js";