Fix mpv pause state when loading new media

Fixes #107

This fixes an issue where loading a new media URL while the player
was paused would keep playback paused, causing Music Assistant to
show the player as playing while no audio was audible.

The mpv pause state is now always set explicitly when starting playback,
ensuring deterministic behavior

linux_voice_assistant/player/libmpv.py

@@ -0,0 +1,86 @@
+import threading
+import logging
+from .base import AudioPlayer
+from .state import PlayerState
+import mpv
+
+
+class LibMpvPlayer(AudioPlayer):
+
+    def __init__(self, device: str | None = None):
+        self._log = logging.getLogger(self.__class__.__name__)
+        self._state = PlayerState.IDLE
+        self._state_lock = threading.Lock()
+
+        self._last_volume: float = 100.0  # mpv Volume 0-100
+
+        self._mpv = mpv.MPV(
+            audio_display=False,
+            log_handler=self._on_mpv_log,
+            loglevel="error",
+        )
+        if device:
+            self._log.info("Using audio device: %s", device)
+            self._mpv["audio-device"] = device
+
+    # -------- Core Methods --------
+
+    def play(self, url: str, paused: bool = False) -> None:
+        with self._state_lock:
+            self._set_state(PlayerState.LOADING)
+
+        self._mpv.pause = paused
+
+        self._log.info("Loading media: %s (paused=%s)", url, paused)
+        self._mpv.play(url)
+
+    def pause(self):
+        with self._state_lock:
+            self._mpv.pause = True
+            self._set_state(PlayerState.PAUSED)
+
+    def resume(self):
+        with self._state_lock:
+            self._mpv.pause = False
+            self._set_state(PlayerState.PLAYING)
+
+    def stop(self):
+        with self._state_lock:
+            self._mpv.stop()
+            self._set_state(PlayerState.IDLE)
+
+    def state(self):
+        with self._state_lock:
+            return self._state
+
+    # -------- Volume / Ducking --------
+
+    def set_volume(self, volume: float):
+        """
+        volume: float 0.0-1.0
+        """
+        with self._state_lock:
+            self._last_volume = volume * 100
+            self._mpv.volume = self._last_volume
+
+    def duck(self, factor: float = 0.5):
+        with self._state_lock:
+            self._last_volume = getattr(self, "_last_volume", self._mpv.volume)
+            self._mpv.volume = self._last_volume * factor
+
+    def unduck(self):
+        with self._state_lock:
+            self._mpv.volume = getattr(self, "_last_volume", self._mpv.volume)
+
+    # -------- Internal Helpers --------
+
+    def _on_mpv_log(self, level, prefix, text):
+        if level in ("error", "fatal"):
+            self._log.error("[mpv] %s", text.strip())
+            with self._state_lock:
+                self._set_state(PlayerState.ERROR)
+
+    def _set_state(self, new_state: PlayerState):
+        if self._state != new_state:
+            self._log.debug("State %s → %s", self._state.name, new_state.name)
+            self._state = new_state