Save CLI results with their own file extension, not the input's #587

Why

When an Assembly turns one input into a result with a different type, the CLI saves the result under the input's filename and extension. A /video/thumbs Step on social.mp4 with -o out/ wrote a JPEG to out/…/social.mp4; a builtin/transcribe run saved its JSON as ….mp4. Opening those files fails or confuses tools, and users can't tell what they got.

Seen with @transloadit/node 6.1.2 on 2026-10-18.

Proposal

• Name downloaded results by the result's own name/ext (or the input basename plus the result's extension), not the input's extension.
• Keep the existing directory layout (<input>/<step>/…) so scripts don't break, and add a test with a type-changing Step (video → jpg, video → json).

_{🤖 Released by kvz on framework1/content-clone-10 since 2026-10-18 · resume: claude --resume e0b6ec91-9333-451d-94f2-93dea1b12f72}