UI redesign: consistent design system, card layout, unified colors and typography

Refactor: split panels into pure logic + UI layers

Comment out new features (CLIP×φ sort, λ input, brain MEI sidecar) until ready

Sort by CLIP×φ, per-feature λ input, brain MEI sidecar support, gallery in UI

Fix multi-session crash: match modules by file path, not __package__

Fix multi-session module clearing: also remove parent package attribute

Fix multi-session crash: clear Bokeh widget modules between sessions

Switch to modular explorer package (scripts/explorer/)