VPA: support non-time-resolved (fMRI) data
- evaluate accepts a no-time dependent (2D array or list of
- per-subject RDMs) and returns per-subject (squeezed) results
- fix evaluate_3 unpacking VPA_3's dict (was assigning keys)
- accept bare-string independents, not only lists
- surface the noise ceiling (UNC/LNC) in the dataframe and plots
- use Spearman for the noise ceiling per the docstrings
- add Plotting.plotting_components for no-time results; guard
- plotting_over_time and tidy its legend
Note: results now include UNC/LNC rows and noise-ceiling values
change (Pearson -> Spearman).