v0.2.3 — MCP Registry readiness

• MCP Registry: README carries the mcp-name validation marker and
  server.json (current registry schema) sits at the repo root — Veracium is
  publishable to registry.modelcontextprotocol.io, which the MCP directories
  crawl. docs/mcp.md refreshed: PyPI install flow (the page still described
  a pre-PyPI clone install), the remember tool row now documents
  derived_from, recall documents token_budget, and the deliberately
  non-MCP verbs are listed with their rationale.