[s8n-anton]

Fixes two issues with shell-by-shell shotgun reloads:

• Reloading an empty weapon could stop after chambering the first shell instead of continuing to fill the magazine;
• Cancelling an insertion could count the unfinished shell as loaded. Repeated fire-button clicks could also skip reload stages.

Fire input now cancels opening or insertion without adding a shell, then plays the closing animation. Shells already inserted at animation motion marks are kept. Further clicks during closing do not add ammunition, restart closing or fire the weapon.