Validate output table window bounds

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Summary

• reject feature and alert output rows where window_end is not after window_start
• reject alert rows whose alert_time falls outside their window bounds
• add output table validation coverage for bad window ranges and out-of-window alerts

Tests

• pytest tests/test_io.py tests/test_cli_errors.py tests/test_pipeline_e2e.py
• pytest
• python -m telemetry_window_demo.cli run --config configs/default.yaml