VAULT: Persistent agent memory — the KEY tool. Store and retrieve data across sessions. Agents are stateless — use this to remember facts, preferences, task state, API keys, conversation summaries, and configuration between runs. Data persists indefinitely in KV storage. Once stored, data is yours forever — only accessible through this server. Call with action='get' to read, action='set' to write, action='delete' to remove, action='search' to find by keyword.