docs: fix macrostate counts and simulation time in plots.md captions

[biofe]

Summary

• Update macrostate counts from 12 → 14 in all HP35 example captions that use the reduced test dataset (dendrogram, sankey, contacts, macrotraj, state network, transition matrix, transition time)
• Sankey caption: "14 vs 12" → "14 vs 14" (both KL/none and T/none reference give 14 macrostates from test data)
• Macrostate trajectory caption: ~60 µs → ~300 µs
• Intro paragraph: note that most examples use the reduced test dataset (14 macrostates); CK test uses the full dataset (12 macrostates)
• CK test caption unchanged (correctly shows 12 macrostates from full data)