v0.6.1

Added

• display_name / display_description on tool definitions and bindings.
  Optional consumer-only metadata, accepted by register_service_tool /
  register_selector_tool / register_chain_tool, by
  ToolDefinition.service() / .selector() (and forwarded through
  register_tools), and carried onto the resulting ToolBinding /
  SelectorToolBinding / ChainToolBinding. The MCP server never emits
  them on the wire (tools/list ignores them) — they exist so a downstream
  library can render a richer label / blurb than the protocol title /
  description. Both default to None.