fix(terminal): resolve TypeScript error for oscillator.start() call (#344)

- Fixed TS2554 error where oscillator.start() expected 1-2 arguments but got 0
- The Web Audio API's start() method requires an explicit when parameter
- Changed oscillator.start() to oscillator.start(audioContext.currentTime)
  for explicit timing aligned with oscillator.stop()

This fixes the terminal bell sound functionality while resolving the
TypeScript compilation error.

Co-authored-by: Droid Agent <droid@factory.ai>

Author: echobt

cortex-gui/src/components/TerminalPanel.tsx

@@ -1299,7 +1299,7 @@ export function TerminalPanel() {
           oscillator.frequency.value = 800;
           oscillator.type = "sine";
           gainNode.gain.value = 0.1;
-          oscillator.start();
+          oscillator.start(audioContext.currentTime);
           oscillator.stop(audioContext.currentTime + 0.1);
         } catch (e) {
           console.warn("[Terminal] Failed to play bell sound:", e);