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/brave-search.toml

@@ -0,0 +1,28 @@
+id = "brave-search"
+name = "Brave Search"
+description = "Perform web searches using the Brave Search API through the MCP server"
+category = "ai"
+icon = "🦁"
+tags = ["search", "web", "brave", "api", "information-retrieval"]
+
+[transport]
+type = "stdio"
+command = "npx"
+args = ["-y", "@modelcontextprotocol/server-brave-search"]
+
+[[required_env]]
+name = "BRAVE_API_KEY"
+label = "Brave Search API Key"
+help = "An API key from the Brave Search API dashboard"
+is_secret = true
+get_url = "https://brave.com/search/api/"
+
+[health_check]
+interval_secs = 60
+unhealthy_threshold = 3
+
+setup_instructions = """
+1. Go to https://brave.com/search/api/ and sign up for a Brave Search API plan (free tier available).
+2. Generate an API key from your Brave Search API dashboard.
+3. Paste the API key into the BRAVE_API_KEY field above.
+"""