feat: sync content definitions from core repo

Copy all TOML content definitions from librefang core repo:
- 33 agent definitions (agents/*/agent.toml)
- 14 hand definitions with docs (hands/*/HAND.toml + SKILL.md)
- 25 integration templates (integrations/*.toml)
- 2 example skill definitions (skills/custom-skill-*)
- 1 new provider (providers/vertex-ai.toml)

Part of the framework-vs-content registry split (RFC v0.7).

integrations/discord-mcp.toml

@@ -0,0 +1,28 @@
+id = "discord-mcp"
+name = "Discord"
+description = "Access Discord servers, channels, and messages through the MCP server"
+category = "communication"
+icon = "🎮"
+tags = ["chat", "messaging", "community", "gaming", "voice"]
+
+[transport]
+type = "stdio"
+command = "npx"
+args = ["-y", "mcp-discord"]
+
+[[required_env]]
+name = "DISCORD_BOT_TOKEN"
+label = "Discord Bot Token"
+help = "A bot token from the Discord Developer Portal"
+is_secret = true
+get_url = "https://discord.com/developers/applications"
+
+[health_check]
+interval_secs = 60
+unhealthy_threshold = 3
+
+setup_instructions = """
+1. Go to the Discord Developer Portal (https://discord.com/developers/applications) and create a new application.
+2. Navigate to the 'Bot' section, click 'Add Bot', and copy the bot token.
+3. Invite the bot to your server using the OAuth2 URL generator with the required permissions, then paste the token into the DISCORD_BOT_TOKEN field above.
+"""