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/gcp-mcp.toml

@@ -0,0 +1,28 @@
+id = "gcp-mcp"
+name = "Google Cloud Platform"
+description = "Manage GCP resources including Compute Engine, Cloud Storage, and BigQuery through the MCP server"
+category = "cloud"
+icon = "🌐"
+tags = ["cloud", "google", "infrastructure", "gce", "gcs", "bigquery", "devops"]
+
+[transport]
+type = "stdio"
+command = "npx"
+args = ["-y", "@google-cloud/gcloud-mcp"]
+
+[[required_env]]
+name = "GOOGLE_APPLICATION_CREDENTIALS"
+label = "Service Account Key Path"
+help = "Absolute path to a GCP service account JSON key file"
+is_secret = false
+get_url = "https://console.cloud.google.com/iam-admin/serviceaccounts"
+
+[health_check]
+interval_secs = 60
+unhealthy_threshold = 3
+
+setup_instructions = """
+1. Go to the GCP Console > IAM & Admin > Service Accounts (https://console.cloud.google.com/iam-admin/serviceaccounts) and create a new service account with the necessary roles.
+2. Generate a JSON key file for the service account and save it to a secure location on your filesystem.
+3. Enter the absolute path to the JSON key file in the GOOGLE_APPLICATION_CREDENTIALS field above.
+"""