Clean outcome coding for multi-study papers (incl. recode xphi from reports)

Currently, the outcome coding for many multi-study papers is displayed messily, and not ready for public display.

For instance, xphi refers to the dataset, rather than the linked invidual reports. This should be coded directly from the reports

No file, test, or entry point is named in the issue. First locate the outcome-coding data for multi-study papers and trace how xphi currently points to the dataset rather than individual reports; done means the coding is clean for public display and xphi is recoded from the linked reports.

Written by the indexing model from the issue text.