[Week 11–12] neurosim.plot: UMAP visualisation + publication figure generation

[TheRoy666]

plot.py is implemented with 7 functions and 27 tests passing. This issue
tracks the real-data figure generation for the methods paper.

Tasks:

• Install umap-learn and verify plot_state_space() uses UMAP on real data
• Generate 6-panel summary figure (plot_neurosim_summary) on HCP subject
• Generate cohort energy violin plot (plot_cohort_energy) for AUD results
• Generate stimulation target ranking (plot_stimulation_targets) for epilepsy SOZ
• Verify all figures save correctly as PNG + PDF at 300 DPI
• Draft Figure 1 and Figure 2 for methods paper

Tracks GSoC Weeks 11–12 deliverable.