v0.6.2

fix(security): guard FastMCP-core not-found reflection on the router aggregator — unknown tool/resource/prompt names (incl. via the call_tool meta-tool), malformed-request records, and AggregateProvider provider-fault logs no longer reach any caller-visible field or server log; unresolved tool names are bucketed to _unknown in the structlog audit sink and Prometheus labels so a grammar-valid-but-nonexistent name cannot inject into operator logs/metrics. Also marks the Response-Envelope Standard v1.1 §Error-message-sanitation fast-follow COMPLETE fleet-wide (21 backends + router). Patch, no schema change. Research use only; not clinical decision support.