buildInterior returns room.audio = { musicKey, toneKey }, seeded per shop: keys into Lane E's manifest.audio (interior music bed + room-tone). Lane F's interior_mode plays it, B's audio.js resolves keys->files. Keys not files: buildInterior stays synchronous + asset-free; silence on missing/mute/noassets (house audio law).
Maps mirror the manifest per-type types arrays: record/milkbar/video/dept/arcade always play their bed; other types room-tone-only except a seeded ~1-in-3 general radio (the 'general'-tagged milk-bar bed).
Verified 9 types x 8 seeds: 0 bad keys, 0 nondeterminism, all keys resolve + match manifest type membership, deterministic per shop. Contract + F wiring: docs/LANES/LANE_C_AUDIO.md.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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