Improve bestiary portrait layout

[Daren9m]

Summary

• give the selected creature five of twelve desktop columns instead of one third
• constrain the sticky detail panel to the viewport and let long stat blocks scroll
• replace wide, heavily cropped card banners with compact 4:5 side portraits
• adjust card-grid breakpoints so narrower desktop result columns remain readable

Why

The generated assets use a 4:5 portrait composition, but the previous 5:3 thumbnail frame cropped away most of each creature. Image-bearing cards also stretched neighboring text-only cards into large empty panels, while the selected creature panel was too narrow for the artwork.

Impact

Portraits retain their intended framing, the selected artwork is substantially larger, and long stat blocks remain usable through an independent scroll region.

Validation

• focused ESLint — passed
• staged diff check — passed
• live browser verification at 1600×1000 — no console errors
• selected portrait measured 490×613; card portraits measured 128×160
• selected panel overflow verified with viewport-height scrolling

Full local typecheck remains blocked by unrelated untracked puzzle-engine files with unresolved imports. Those files and the concurrent production image batch are not included in this PR.