Fix: Capture error from turn_end event in agent state

Previously, errors in turn_end events (e.g., from OpenRouter Auto Router)
were not captured in agent.state.error, making failed requests appear as
successful completions.

Fixes #6

packages/agent/CHANGELOG.md

@@ -0,0 +1,11 @@
+# Changelog
+
+## [0.7.6] - Unreleased
+
+### Fixed
+
+- Fixed error message loss when `turn_end` event contains an error. Previously, errors in `turn_end` events (e.g., "Provider returned error" from OpenRouter Auto Router) were not captured in `agent.state.error`, making it appear as if the agent completed successfully. ([#6](https://github.com/badlogic/pi-mono/issues/6))
+
+## [0.7.5] - 2025-11-13
+
+Previous releases did not maintain a changelog.