[Issue]: Microphone remains active after Aptune quits during input switch

[yyovil]

Expected behavior

If Aptune exits because the input-source switch fails, it should fully stop audio capture and release the microphone instead of leaving the mic active.

Actual behavior

After Aptune quits abruptly during the Bluetooth-mic to built-in-mic switch described in #2, the microphone is still on.

Steps to reproduce

1. Start Aptune while the active capture/input source is a Bluetooth microphone.
2. Run the Spotlight launcher Aptune Built-in Mic so Aptune switches back to the Mac's built-in microphone.
3. Observe Aptune quit abruptly.
4. Check the microphone state immediately afterward.
5. Observe that the microphone is still on even though Aptune has exited.

Environment

Same environment as #2:
macOS 26.3.1 (25D2128)
MacBook Air (Apple M4, Mac16,12)
Spotlight launcher installed with aptune install-plugin built-in-mic
Launcher used: Aptune Built-in Mic

Suggested prompt

Investigate why Aptune leaves the microphone active after the abrupt termination reported in #2. Review the shutdown and cleanup path around input rerouting and aptune use-built-in-mic --replace-running to ensure the capture session is torn down and the input device is released when Aptune exits unexpectedly.