Replace repo topics with tags people actually search

[dcwhite]

Tier 0 — mechanical, ~15 minutes.

Our 16 repo topics are honest but unsearched. Measured repo counts per topic:

Current topic	Repos carrying it
scientific-computations	nonstandard — canonical scientific-computing has 3,986
boost-libraries	negligible
forward-problem	negligible
linear-systems	negligible
cmake, open-source, qt5	generic / superseded

Meanwhile the tags our peers actually use, and that users actually browse:

Proposed topic	Repos
simulation	24,636
medical-imaging	5,125
scientific-computing	3,986
eeg	2,137
dicom	1,172
neuroimaging	1,063
ecg	860
computational-neuroscience	717
finite-element-analysis	593
visual-programming	520
biomedical-engineering	441
electrophysiology	364

Slicer carries medical-imaging, neuroimaging, medical-image-computing, segmentation, registration, itk, vtk. We carry none of them.

Action

Keep 9, drop 7, add 11 (GitHub's cap is 20):

gh api -X PUT repos/SCIInstitute/SCIRun/topics \
  -f names[]=biomedical -f names[]=c-plus-plus -f names[]=dataflow-programming \
  -f names[]=inverse-problems -f names[]=mesh-generation -f names[]=python \
  -f names[]=qt6 -f names[]=scientific-visualization -f names[]=visualization \
  -f names[]=scientific-computing -f names[]=medical-imaging -f names[]=neuroimaging \
  -f names[]=computational-neuroscience -f names[]=electrophysiology -f names[]=eeg \
  -f names[]=ecg -f names[]=finite-element-analysis -f names[]=simulation \
  -f names[]=visual-programming -f names[]=biomedical-engineering

Dropped: boost-libraries, cmake, open-source, scientific-computations, qt5, linear-systems, forward-problem.

Add vtk in place of one of these once the VTK renderer branch lands.