Log CPU-usage for each line/function individually

Hi, Kudos to this amazing work.

I am using this tool and ask if it is possible to get the line by line or function-wise CPU usage rather than the overall stats.

Start by reviewing how psrecord currently gathers and reports overall CPU usage. Determine whether line-level or function-level measurements are supported by the existing approach, and define the expected output and scope before implementation. Done should provide per-line or per-function CPU usage rather than only process-wide statistics.

Written by the indexing model from the issue text.