• Fixes MCP heading targeting being unusable from clients that do not
  resolve anyOf parameter schemas: vault_read and vault_patch now accept
  a heading target that arrives as the JSON-encoded text of an array
  (or "null" for vault_patch's document root), and the bare-string
  rejection now explains that the client may not support anyOf-typed
  tool parameters instead of blaming the caller. (#315; thanks
  @yoshihiro-saita for the excellent diagnosis and @MarkDiGiovanni for
  confirming!)