Update octave range and velocity settings per user request

- Add C2 octave and remove C8 (now C2-C7 range instead of C3-C8)
- Set velocity override checkbox checked by default
- Set default velocity slider value to 20 instead of 80
- Update checkbox initialization to respect default parameter override states

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

gui/arpeggiator_controls.py

@@ -67,7 +67,7 @@ class ArpeggiatorControls(QWidget):
             'note_speed': False,
             'gate': False,
             'swing': False,
-            'velocity': False,
+            'velocity': True,
             'tempo': False,
             'delay_enabled': False,
             'delay_length': False,
@@ -238,6 +238,10 @@ class ArpeggiatorControls(QWidget):
         checkbox.setToolTip(f"Override {text} - when checked, presets won't change this parameter")
         checkbox.stateChanged.connect(lambda state, param=param_name: self.on_parameter_override_changed(param, state == 2))
         
+        # Set checkbox state based on default override value
+        if self.parameter_overrides.get(param_name, False):
+            checkbox.setChecked(True)
+        
         # Create label
         label = QLabel(text)
         
@@ -321,7 +325,7 @@ class ArpeggiatorControls(QWidget):
         octave_layout.setSpacing(0)  # NO spacing between buttons
         octave_layout.setContentsMargins(0, 0, 0, 0)
         
-        for octave in range(3, 9):  # C3 to C8
+        for octave in range(2, 8):  # C2 to C7
             btn = self.create_scalable_button(f"C{octave}", 50, 22, 12, checkable=True,
                                             style_type="active" if octave == 4 else "normal")
             btn.clicked.connect(lambda checked, o=octave: self.on_octave_clicked(o))
@@ -602,10 +606,10 @@ class ArpeggiatorControls(QWidget):
         velocity_layout.addWidget(self.create_parameter_label_with_override("Velocity:", "velocity"))
         self.velocity_slider = QSlider(Qt.Horizontal)
         self.velocity_slider.setRange(1, 127)
-        self.velocity_slider.setValue(80)
+        self.velocity_slider.setValue(20)
         self.velocity_slider.setFixedHeight(25)
         velocity_layout.addWidget(self.velocity_slider)
-        self.velocity_label = QLabel("80")
+        self.velocity_label = QLabel("20")
         self.velocity_label.setFixedWidth(40)
         velocity_layout.addWidget(self.velocity_label)
         layout.addLayout(velocity_layout)