Connect to Discord, switch to NVIDIA NIM providers

- Enable Discord channel, respond to all messages from allowed users
- Switch all agents to NVIDIA NIM (Kimi K2.5, DeepSeek V3.1)
- Auto-approve all tools for non-interactive Docker deployment
- Fix tool call arguments serialization (dict → JSON string)
- Fix Dockerfile to copy source before uv sync

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

xtrm_agent/channels/discord.py

@@ -45,16 +45,10 @@ class DiscordChannel(BaseChannel):
             if message.author.bot:
                 return
 
-            # Check allowlist
+            # Check allowlist — if set, only respond to listed users
             if self.allowed_users and str(message.author.id) not in self.allowed_users:
                 return
 
-            # Only respond to mentions or DMs
-            is_dm = isinstance(message.channel, discord.DMChannel)
-            is_mentioned = self.client.user in message.mentions if self.client.user else False
-            if not is_dm and not is_mentioned:
-                return
-
             content = message.content
             # Strip bot mention from content
             if self.client.user: