Drop archive.org at runtime: local-first found audio + video

The live app streamed found sounds and background video straight from archive.org, which CORS-blocked and 500'd in the browser (Safari). Now the runtime prefers the local cache and never touches archive.org for anything we have on disk.

• found-manifest.json maps each archive source URL -> local found/.wav; found-player.decodeUrlToBuffer resolves local FIRST, archive only as a warned fallback.

• video-layer srcFor prefers kind:"local" when the clip is cached; archive "remote" only for clips with no local file.

• fetch-found-video-catalog.sh caches the 97 archive-only av_* cue-windows (~124MB, range-seeked) so all 231 catalog clips play local; clips.json + the mp4s stay gitignored (derived).

Verified: headless: found decodes from found/*.wav, video from found/video/*, zero archive.org requests for any cached asset.

▶ Play it: Rail Replacement Rapture — a bed-heavy genre where the found-sound layer carries the room https://stellate.app/?genre=transitwave&seed=9087&path=749.12536,768.12569,730.12569&xdur=13.122

1638b4e https://github.com/aboard-io/stellate/commit/1638b4ef4aa41adaf87d768483bbbd244355ff77