docs: add missing bug fixes to v0.1.13 changelog

Include the three bug fixes that were merged but not documented:
- #388: Faster CLI error propagation
- #385: Pydantic 2.12+ compatibility
- #391: Concurrent subagent write lock

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: ashwin-ant

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 ## 0.1.13
 
+### Bug Fixes
+
+- **Faster error handling**: CLI errors (e.g., invalid session ID) now propagate to pending requests immediately instead of waiting for the 60-second timeout (#388)
+- **Pydantic 2.12+ compatibility**: Fixed `PydanticUserError` caused by `McpServer` type only being imported under `TYPE_CHECKING` (#385)
+- **Concurrent subagent writes**: Added write lock to prevent `BusyResourceError` when multiple subagents invoke MCP tools in parallel (#391)
+
 ### Internal/Other Changes
 
 - Updated bundled Claude CLI to version 2.0.59