v3.15.0

Fixed & improved

• Onboarding shows once — adding a new clip no longer restarts the tour. The empty screen is now a clean centered paste-a-URL / Add file (no video, no sample button).
• Try sample removed from the editor (it's part of onboarding only).
• Start tour button restyled (rounded, soft glow — less blocky); 'Skip' is plain.
• Anything that needs a clip (player, scrubber, volume, crop/export, overrides) is greyed until you load one.
• Options scroll when the window is too short.
• New Audio fade length control (0.25 / 0.5 / 1s).
• Scrubber playback stays within your trim in/out bounds.
• Normalize is now a clean On/Off toggle; fixed the clipped 'Original' button.