feat(ui): m6 polish — in-memory history sidebar + _safe_call error wrapper

feat(post): wire separate stems / normalise / mp3 export buttons in output panel (m5 g2)

feat(ui): wire lyrics tab + cross-tab use-in-generate handoff (m4)

feat(ui): wire cover/extend/edit tabs into the sidebar layout (m3 e3+e4)

feat(ui): wire single-lora picker into generate tab (m2 d5)

fix(ui): kill .styler bands + label icons + deepen pill contrast

fix(ui): full Brutalist Mono retheme — IBM Plex, padding crush, scoped selectors

fix(ui): wireframe-fidelity polish — neutral palette, mobile single-row, tight chrome

fix(ui): mobile sidebar — compact tab pills, kill dead vertical chrome

fix(ui): inline-muted component labels + drop broken tablet rail mode

fix(ui): replace gr.Tabs with sidebar nav per wireframes

chore(fmt): apply ruff format and remove unused import in conftest

feat(ui): add brutalist mono theme tokens and responsive css