Add mic ON/OFF toggle, headphone and studio output busses

- Channels 0-1 are now dedicated Mic 1/Mic 2 with mic_on toggle
- Mic audio only routes to main when mic_on=True, never to headphone
- New headphone_out_L/R JACK ports (all channels except mics)
- New studio_out_L/R JACK ports (copies main, mutes when any mic is on)
- Mic ON/OFF toggle button in mixer UI (hidden on non-mic channels)
- Session save/load includes mic_on state

mixer_widget.py

@@ -9,7 +9,7 @@ from PySide6.QtCore import Qt, QTimer, QSize
 from PySide6.QtGui import QFont, QPainter, QColor, QLinearGradient, QPen
 
 from audio_engine import NUM_MIXER_CHANNELS
-from icons import icon_mute, icon_solo
+from icons import icon_mute, icon_solo, icon_mic
 import math
 
 
@@ -214,6 +214,28 @@ class ChannelStrip(QFrame):
         """)
         btn_row.addWidget(self.solo_btn)
 
+        # Mic ON/OFF button for channels 0 and 1
+        self.mic_btn = QPushButton()
+        self.mic_btn.setFixedSize(28, 24)
+        self.mic_btn.setIconSize(QSize(16, 16))
+        self.mic_btn.setIcon(icon_mic("#888"))
+        self.mic_btn.setCheckable(True)
+        self.mic_btn.setToolTip("Mic ON – audio goes to main")
+        self.mic_btn.setStyleSheet("""
+            QPushButton {
+                background-color: #202426;
+                border: 1px solid #303a3a;
+                border-radius: 3px;
+            }
+            QPushButton:checked {
+                background-color: #1a3a1a;
+                border: 1px solid #00cc66;
+            }
+            QPushButton:hover { background-color: #303436; }
+        """)
+        self.mic_btn.setVisible(self.channel_index < 2)
+        btn_row.addWidget(self.mic_btn)
+
         self.pfl_btn = QPushButton("PFL")
         self.pfl_btn.setFixedSize(28, 24)
         self.pfl_btn.setFont(QFont("Segoe UI", 7, QFont.Bold))
@@ -242,6 +264,7 @@ class ChannelStrip(QFrame):
         self.volume_slider.valueChanged.connect(self._on_volume_changed)
         self.mute_btn.toggled.connect(self._on_mute_toggled)
         self.solo_btn.toggled.connect(self._on_solo_toggled)
+        self.mic_btn.toggled.connect(self._on_mic_toggled)
         self.pfl_btn.toggled.connect(self._on_pfl_toggled)
 
     def _rename(self):
@@ -266,9 +289,17 @@ class ChannelStrip(QFrame):
     def _on_pfl_toggled(self, checked: bool):
         self.engine.set_channel_pfl(self.channel_index, checked)
 
+    def _on_mic_toggled(self, checked: bool):
+        self.engine.set_channel_mic_on(self.channel_index, checked)
+        color = "#00cc66" if checked else "#888"
+        self.mic_btn.setIcon(icon_mic(color))
+
     def _refresh(self):
         self.vu_meter.set_value(self._channel.vu_peak)
         self.volume_slider.setValue(int(math.sqrt(self._channel.volume) * 100))
+        if self.channel_index < 2:
+            color = "#00cc66" if self._channel.mic_on else "#888"
+            self.mic_btn.setIcon(icon_mic(color))
 
 
 class MasterPreSection(QFrame):