Cleanup: delete the umiwashi reel + 340MB of derived render outputs

At Paul's direction ("delete unused data and old wavs"): the flagged 1943 propaganda reel is deleted from found/video/lib/ (86MB, never cued; SOURCES.md row replaced with a tombstone, cut-lib-clips.sh entry pruned to a comment), along with all regenerable derived audio

• Cross-referenced every found/ file against all live registries (genre-kernel SOURCES/SAMPLES/GENRE_CLIPS/stationPool, sample manifest, clip manifests, fetch recipes): no orphaned found audio exists

• Total freed this round ~340MB (+ 840MB grand tour in 1461353). verify.sh PASS after deletion — no live registry lost a file.

▶ Play it: Rail Replacement Rapture — a bed-heavy genre where the found-sound layer carries the room https://stellate.app/?genre=transitwave&seed=1425&path=749.12536,768.12569,730.12569&xdur=13.122

47f24f9 https://github.com/aboard-io/stellate/commit/47f24f99a9ff5373142dc199209c050c5106d290