feat: add /voice preview command

- Added 8 random preview sample lines for voice testing
- New /voice preview <name> command to hear voices before selecting
- Previews play in queue like regular messages (no queue jumping)
- Preview does NOT change user's active voice preference
- Updated queue system to support voice override for previews
- Added documentation for new command in README

bot.py

@@ -1,5 +1,6 @@
 __version__ = "1.1.0"
 
+import random
 import sys
 import os
 
@@ -30,6 +31,18 @@ from voice_manager import VoiceManager
 # Inactivity timeout in seconds (10 minutes)
 INACTIVITY_TIMEOUT = 10 * 60
 
+# Sample lines for voice preview
+PREVIEW_LINES = [
+    "Hello! This is how I sound. Choose me as your voice with /voice set.",
+    "Testing, one, two, three! Can you hear me clearly?",
+    "Here's a preview of my voice. Pretty cool, right?",
+    "Greetings! I am ready to speak for you.",
+    "Voice check! This is what I sound like.",
+    "Audio test complete. This voice is ready to go!",
+    "Sample message incoming. How do I sound to you?",
+    "Preview mode activated. Testing speech synthesis.",
+]
+
 
 class TTSBot(commands.Bot):
     """Discord bot that reads messages aloud using Pocket TTS."""
@@ -41,7 +54,7 @@ class TTSBot(commands.Bot):
         super().__init__(command_prefix="!", intents=intents)
 
         self.voice_manager = VoiceManager(Config.VOICES_DIR, Config.DEFAULT_VOICE)
-        self.message_queue: asyncio.Queue[tuple[discord.Message, str]] = asyncio.Queue()
+        self.message_queue: asyncio.Queue[tuple[discord.Message, str] | tuple[discord.Message, str, str]] = asyncio.Queue()
         self.last_activity: float = 0.0
         
         self._setup_slash_commands()
@@ -59,6 +72,7 @@ class TTSBot(commands.Bot):
             app_commands.Choice(name="set", value="set"),
             app_commands.Choice(name="current", value="current"),
             app_commands.Choice(name="refresh", value="refresh"),
+            app_commands.Choice(name="preview", value="preview"),
         ])
         async def voice_command(
             interaction: discord.Interaction,
@@ -73,6 +87,8 @@ class TTSBot(commands.Bot):
                 await self._handle_voice_current(interaction)
             elif action.value == "refresh":
                 await self._handle_voice_refresh(interaction)
+            elif action.value == "preview":
+                await self._handle_voice_preview(interaction, voice_name)
         
         @voice_command.autocomplete("voice_name")
         async def voice_name_autocomplete(
@@ -206,6 +222,66 @@ class TTSBot(commands.Bot):
             ephemeral=True
         )
 
+    async def _handle_voice_preview(self, interaction: discord.Interaction, voice_name: str | None) -> None:
+        """Handle /voice preview command."""
+        if not voice_name:
+            await interaction.response.send_message(
+                "❌ Please provide a voice name. Use `/voice list` to see available voices.",
+                ephemeral=True
+            )
+            return
+        
+        # Check if user is in a voice channel
+        if interaction.user.voice is None:
+            await interaction.response.send_message(
+                "❌ You need to be in a voice channel to hear a preview!",
+                ephemeral=True
+            )
+            return
+        
+        voice_name = voice_name.lower()
+        
+        # Validate voice exists
+        if not self.voice_manager.is_voice_available(voice_name):
+            voices = self.voice_manager.get_available_voices()
+            await interaction.response.send_message(
+                f"❌ Voice `{voice_name}` not found.\n"
+                f"Available voices: {', '.join(f'`{v}`' for v in voices)}",
+                ephemeral=True
+            )
+            return
+        
+        # Select a random preview line
+        preview_text = random.choice(PREVIEW_LINES)
+        
+        # Create a preview message object with all necessary attributes
+        class PreviewMessage:
+            def __init__(self, user, channel, voice_channel):
+                self.author = user
+                self.channel = channel
+                self._voice_channel = voice_channel
+            
+            @property
+            def voice(self):
+                class VoiceState:
+                    def __init__(self, channel):
+                        self.channel = channel
+                return VoiceState(self._voice_channel)
+        
+        preview_message = PreviewMessage(
+            interaction.user,
+            interaction.channel,
+            interaction.user.voice.channel
+        )
+        
+        # Queue the preview with voice override
+        await self.message_queue.put((preview_message, preview_text, voice_name))
+        
+        await interaction.response.send_message(
+            f"⏳ Queued preview for `{voice_name}`. Sample: \"{preview_text[:50]}{'...' if len(preview_text) > 50 else ''}\"",
+            ephemeral=True
+        )
+
     async def setup_hook(self) -> None:
         """Called when the bot is starting up."""
         print("Initializing TTS...")
@@ -258,16 +334,23 @@ class TTSBot(commands.Bot):
     async def process_queue(self) -> None:
         """Process messages from the queue one at a time."""
         while True:
-            message, text = await self.message_queue.get()
+            queue_item = await self.message_queue.get()
+            
+            # Handle both regular messages (message, text) and previews (message, text, voice_name)
+            if len(queue_item) == 3:
+                message, text, voice_override = queue_item
+            else:
+                message, text = queue_item
+                voice_override = None
 
             try:
-                await self.speak_message(message, text)
+                await self.speak_message(message, text, voice_override)
             except Exception as e:
                 print(f"Error processing message: {e}")
             finally:
                 self.message_queue.task_done()
 
-    async def speak_message(self, message: discord.Message, text: str) -> None:
+    async def speak_message(self, message: discord.Message, text: str, voice_override: str | None = None) -> None:
         """Generate TTS and play it in the user's voice channel."""
         if message.author.voice is None:
             return
@@ -280,18 +363,24 @@ class TTSBot(commands.Bot):
 
         print(f"Generating TTS for: {text[:50]}...")
         
-        # Get user's voice (loads on-demand if needed)
-        user_id = message.author.id
+        # Get voice state (use override for previews, otherwise user's voice)
         try:
-            voice_state = await asyncio.to_thread(
-                self.voice_manager.get_user_voice_state, user_id
-            )
+            if voice_override:
+                voice_state = await asyncio.to_thread(
+                    self.voice_manager.get_voice_state, voice_override
+                )
+            else:
+                user_id = message.author.id
+                voice_state = await asyncio.to_thread(
+                    self.voice_manager.get_user_voice_state, user_id
+                )
         except Exception as e:
-            print(f"Error loading voice for user {user_id}: {e}")
-            await message.channel.send(
-                f"{message.author.mention}, failed to load your voice. Use `/voice set` to choose a voice.",
-                delete_after=5
-            )
+            print(f"Error loading voice: {e}")
+            if not voice_override:
+                await message.channel.send(
+                    f"{message.author.mention}, failed to load your voice. Use `/voice set` to choose a voice.",
+                    delete_after=5
+                )
             return
         
         wav_bytes = await asyncio.to_thread(