Port the useful dynamic-vault MCP direction from Domenico Lupinetti's proposal into the current mounted-workspace model.
Durable external MCP registration is now vault-neutral, Node MCP resolves active mounted vaults from explicit env or Tolaria vaults.json, and vault context includes root AGENTS.md instructions per active vault.
Based-on: https://github.com/refactoringhq/tolaria/pull/603
Co-authored-by: Domenico Lupinetti <domenico@translated.net>
