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/todoist.toml

@@ -0,0 +1,28 @@
+id = "todoist"
+name = "Todoist"
+description = "Manage Todoist tasks, projects, and labels through the MCP server"
+category = "productivity"
+icon = "✅"
+tags = ["tasks", "todo", "project-management", "productivity", "gtd"]
+
+[transport]
+type = "stdio"
+command = "npx"
+args = ["-y", "todoist-mcp"]
+
+[[required_env]]
+name = "TODOIST_API_KEY"
+label = "Todoist API Token"
+help = "Your personal API token from Todoist settings"
+is_secret = true
+get_url = "https://todoist.com/prefs/integrations"
+
+[health_check]
+interval_secs = 60
+unhealthy_threshold = 3
+
+setup_instructions = """
+1. Open Todoist and go to Settings > Integrations > Developer (https://todoist.com/prefs/integrations).
+2. Copy your API token from the 'API token' section.
+3. Paste the token into the TODOIST_API_KEY field above.
+"""