Audio/visual alert when permission prompt is waiting for input (accessibility)

When Claude Code requires user approval for a tool call, there is no audio or system-level notification — the only signal is text appearing in the terminal. For users who step away from their screen while a task runs, this means Claude silently blocks with no way to know it's waiting.

This is also an accessibility concern: users who rely on audio cues, or who have attention or focus difficulties (e.g. ADHD), may not notice a visual-only prompt in a terminal window that isn't in the foreground.

Suggested behaviour:

• Play a system sound when a permission prompt is displayed and waiting for input
• Optionally: send a desktop notification (macOS/Linux notify-send) with the prompt text

Workarounds considered:

• iTerm2 Triggers can approximate this on macOS, but only for iTerm2 users
• A PreToolUse hook fires on every tool call, not specifically when approval is required — so it can't be used to target just the waiting state

A native solution that works in any terminal and on any supported OS would be the right fix.