Update documentation to reflect architectural fixes in the NUMA partition runner and implementation changes in the merge and select modules. The partition runner now wraps task execution in `catch_unwind`, emitting panic events that count toward completion thresholds to prevent controller deadlocks, while re-raising the first payload on return. CLI documentation for select has been updated to mandate output directories, introduce default hard-linking with automatic fallback, and document presence aggregation optimizations. Known issues such as self-merge crashes and sparse-packed index gaps are now documented as failing fast due to these improvements.