Function parse_compute_capability 

pub(crate) fn parse_compute_capability(stdout: &str) -> Option<String>

Parses nvidia-smi --query-gpu=compute_cap stdout ("X.Y\n" or "X.Y\nX.Y\n…" for multi-device queries without -i) into an ORT-compatible smXY string.

Defensive against extra whitespace, trailing newlines, and accidental multi-line output (only the first non-empty line is consumed). Returns None when:

• the input is empty after trimming;
• the first line is not exactly two dot-separated digit components ("X.Y", allowing 1+ digits each so "12.0" parses to "sm120").

Pure: no I/O, no globals. The exhaustive correctness tests in the sibling test module exercise every failure shape so the production invariant (“strict X.Y only”) cannot drift.