Genre build-out 250 -> 273 + accessible type-to-filter combobox

Fill the hollow regions of the genre space via genre-tool delta-scaffolding, every addition refereed by the genre-confusion matrix (stays diagonal-dominant 273/273).

• Named regions (distinct instruments -> open feature-space): 5 classical (romanticism/chamber/impressionism/postminimal/symphony), 4 rock (punk/indie/grunge/postrock), 8 world/latin/jazz/hiphop…

• 6 INVENTED "lerp" genres filling the emptiest midpoints of the 23-D feature space (cryptvespers/nocturnesmash/glacialgabber/breakbop/atticlament/ hazebunker), via the new tools/lerp-genre.js (interpolate two…

• New authoring tools: tools/lerp-genre.js (invent-by-interpolation) and tools/rm-genre.js (clean removal).

• Accessible view (access.html): the three 273-row genre s were unusable, so they become native type-to-filter comboboxes -- one shared + three .

Verified: matrix 273/273, verify.sh (validate/engine/prove/matproof/poscover/ coordscover), full-boot-run, starcruise-run 79/79 + nav, access-ui 12/12.

▶ Play it: Servo Elegy → Ballroom Leviathan → Amen Hypotenuse — the three genres this change names, as one path https://stellate.app/?genre=atticlament&seed=7915&path=1145.12655,814.14156,1206.17398&xdur=0.157

e7d7f53 https://github.com/aboard-io/stellate/commit/e7d7f53b8cb0ca85432a6cc4ca894c64c5ec16ab