Opens a CueCrux session and returns a typed capability plan (retrieval, proofing, memory, journaling, audit) across VaultCrux and MemoryCrux. Call this first, once. Every subsequent action routes through the channels the plan returns — do not browse the legacy per-service tool list when a plan channel already covers the capability. Identical behaviour for local Crux CE and hosted CueCrux. Hosted deployments stage v1 flat-list or v2 typed-graph plan shapes behind feature flags; callers treat the returned plan as the single source of routing truth. Bulk-capable agents transparently use the HTTP/2 binary channel; MCP-only agents use the MCP fallback URLs the plan provides. Implements RCX-Protocol v1.0.