Validate draft x-mcp-header mirroring: every parameter annotated with
x-mcp-header (at any nesting depth) whose value is present in args MUST
have a matching (decoded) Mcp-Param-* header; absent parameters MUST NOT
carry the header. The annotation set itself is also validated against the
draft value constraints (non-empty, HTTP token syntax, no CR/LF, primitive
types only with number forbidden, case-insensitive uniqueness). Returns a
HeaderMismatch exception on violation, else null.
Validate draft x-mcp-header mirroring: every parameter annotated with x-mcp-header (at any nesting depth) whose value is present in args MUST have a matching (decoded) Mcp-Param-* header; absent parameters MUST NOT carry the header. The annotation set itself is also validated against the draft value constraints (non-empty, HTTP token syntax, no CR/LF, primitive types only with number forbidden, case-insensitive uniqueness). Returns a HeaderMismatch exception on violation, else null.