Remove panics from coglet-python setup and mutex locks
- worker_bridge: init_async_loop() and PythonPredictHandler::new() return Result
- input: detect_runtime() returns Result, PreparedInput uses Py<PyDict>
- log_writer: mutex locks use expect() with clear messages
- predictor: handle detect_runtime Result propagation
Worker mutex poisoning now panics with clear message - orchestrator
handles worker exit and fails predictions appropriately.
