Add test profile for Scout with PXD042173

## Summary
Create a 2-file SDRF subset from PXD042173 (DSSO crosslinked recombinant standards) for benchmarking both xiSEARCH and Scout paths.

## Test scenarios
1. `--search_engine xisearch` with SDRF input -> xiFDR -> mzIdentML
2. `--search_engine scout` with SDRF input -> Scout FDR -> mzIdentML
3. Compare results between engines

## Files
- L1_20210727_MxR_FDR_firstbatch_DSSOplate2_B12.raw
- L1_20210727_MxR_FDR_firstbatch_DSSOplate2_E12.raw

Start with the two listed RAW files and trace how SDRF input is passed through the xiSEARCH → xiFDR and Scout FDR paths. Check the existing test-profile setup and compare the resulting mzIdentML outputs; done means both scenarios run successfully on the two-file subset and their results can be compared.

Written by the indexing model from the issue text.