[mikhalchankasm]

MCP schema normalization previously interpreted every JSON field named $ref as a schema reference, including ordinary default/const/enum/examples and custom annotation values. Valid literal remote/missing references could abort catalog initialization, and matching local values were silently rewritten.

Walk only schema keyword positions when collecting/replacing references. Explicit reference targets are still inspected transitively (with cycle protection) and normalized in definition copies, preserving the source instance data. Existing remote/unresolvable-reference rejection and deterministic recursive reference handling remain intact. Closes #211; child of #210.

Validation: 16 regression cases fail on the original implementation; all 38 focused tests pass after the fix with zero skips/warnings. Coverage includes instance data, scalar/array/map/legacy schema slots, recursive and transitive references, invalid actual references and idempotence. Tool-less Claude advisory review identified a deep $defs data-target bypass; Codex reproduced it with three failing cases and corrected it by also relocating deep definition pointers. Direct definition references retain their existing handling. Release2024/2025/2026/2027 x64 L2 passed on final SHA 111f63c; Both CI runs 37190697123 / 37190661065 passed with 2,393 tests and zero skips. The traversal intentionally shares the existing schema-keyword registry; adding dialect keywords such as contentSchema is outside this task, as are pre-existing dangling direct-definition and true-subschema-in-data-target gaps; all three are tracked for verification/fix in #215. No tool contract changes or Navisworks runtime claim.