Bump version to 0.2.0b1 for beta release

Beta includes:
- PID reuse detection for orphaned task cleanup
- Instance tracking (server_id) for crashed process detection
- Proper asyncio.CancelledError handling for sub-agent cancellation
- Shared queue_core.py infrastructure

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: himattm

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "agent-task-queue"
-version = "0.1.4"
+version = "0.2.0b1"
 description = "MCP server for sequential task execution via FIFO queue"
 readme = "README.md"
 requires-python = ">=3.10"