Feature request: let users disable or customize the desktop app's response-completion sound

The Claude desktop app on macOS plays a chime when a response finishes, and there's currently no preference in the app to turn it off or swap it for something else. This is separate from macOS's own notification system: turning off system notifications for Claude in System Settings > Notifications does not stop the sound, because the app plays it directly rather than routing it through Notification Center. That was confirmed independently in #36063, which got auto-closed as off-topic for this repo despite describing the same app.

The current sound is a short, high-pitched chime that reads as harsh rather than a gentle cue, particularly noticeable when running several requests back to back or when the app is left running unattended in the background.

Requested enhancement: add a Notifications or Sound section to the desktop app's preferences with, at minimum, an on/off toggle for the completion sound, and ideally a choice of a few softer alternatives (or a way to point to a custom sound file, similar to how Slack and other desktop apps handle this).

Environment:

• macOS
• Claude desktop app (latest version)