Audio stream starts without MIDI — keyboard mode works standalone

MIDI port is now optional. If no device found or port fails,
the audio stream still starts so keyboard mode works. Cleanup
handles missing MIDI gracefully.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pytheory/live.py

@@ -561,36 +561,38 @@ class LiveEngine:
         ports = self._midi_in.get_ports()
 
         if not ports:
-            print("  No MIDI input ports found.")
-            print("  Connect a MIDI device and try again.")
+            print("  No MIDI input ports found. (Keyboard mode still works)")
             self._midi_in.delete()
             self._midi_in = None
-            return
+            # Don't return — still start audio for keyboard mode
 
-        if port is None:
-            port = 0
-        elif isinstance(port, str):
-            matched = False
-            for i, name in enumerate(ports):
-                if port.lower() in name.lower():
-                    port = i
-                    matched = True
-                    break
-            if not matched:
-                self._midi_in.delete()
-                self._midi_in = None
-                raise ValueError(f"MIDI input port not found: {port!r}")
+        port_name = "none"
+        if self._midi_in and ports:
+            if port is None:
+                port = 0
+            elif isinstance(port, str):
+                matched = False
+                for i, name in enumerate(ports):
+                    if port.lower() in name.lower():
+                        port = i
+                        matched = True
+                        break
+                if not matched:
+                    self._midi_in.delete()
+                    self._midi_in = None
+                    print(f"  MIDI port not found: {port!r}, continuing without MIDI")
+                    port = None
 
-        try:
-            self._midi_in.open_port(port)
-        except Exception:
-            self._midi_in.delete()
-            self._midi_in = None
-            raise
-
-        self._midi_in.ignore_types(sysex=True, timing=False, active_sense=True)
-        self._midi_in.set_callback(self._midi_callback)
-        port_name = ports[port]
+            if self._midi_in and port is not None:
+                try:
+                    self._midi_in.open_port(port)
+                    self._midi_in.ignore_types(sysex=True, timing=False, active_sense=True)
+                    self._midi_in.set_callback(self._midi_callback)
+                    port_name = ports[port]
+                except Exception:
+                    self._midi_in.delete()
+                    self._midi_in = None
+                    print("  Failed to open MIDI port, continuing without MIDI")
 
         print(f"  PyTheory Live Engine")
         print(f"  MIDI: {port_name}")
@@ -620,12 +622,14 @@ class LiveEngine:
         except KeyboardInterrupt:
             print("\n  Stopped.")
         finally:
-            self._stream.stop()
-            self._stream.close()
-            self._stream = None
-            self._midi_in.close_port()
-            self._midi_in.delete()
-            self._midi_in = None
+            if self._stream:
+                self._stream.stop()
+                self._stream.close()
+                self._stream = None
+            if self._midi_in:
+                self._midi_in.close_port()
+                self._midi_in.delete()
+                self._midi_in = None
 
     def keyboard_play(self, ch=1):
         """Enable computer keyboard as MIDI input on a channel."""