Start an app capture: its presigned upload URL.

A capture is an MP4 screen recording of a web app: H.264, constant 30 fps, at most 1920×1080, tagged bt709 (its sound, when it has any, in AAC), up to 512 MB. Every file is checked after its upload; one that does not conform is rejected with the command that re-encodes it. The file never passes through the API: create answers a presigned PUT URL that works for an hour (send exactly the declared bytes with content-type: video/mp4), then finalize checks the stored file and marks the capture ready or rejected (with rejectionReason). Free. The answer's upload is where to PUT the file (with upload.headers); eventsUpload and checkpointUploads are the recorder's side files when declared. Then POST /story-projects/{projectId}/captures/{captureId}/finalize. A capture names the stored tour it ran (tourId, one of this project's tours: its feature is copied onto the capture) and the product feature it shows (featureId, a product Bible episode id — alone, or exactly the tour's own feature); featureName on every read is the feature's name in the Bible as it reads now. Unknown fields are refused with 400 validation_failed. Requires Idempotency-Key.