The sentinel field set by remapToolNamesInRequest() was being included in
the JSON body sent to Anthropic, which rejects unknown top-level fields
with 400 invalid_request_error. Stripped before JSON.stringify in both
code paths:
- buildAndSignClaudeCodeRequest (CC bridge / anthropic-compatible-cc-*)
- base executor serialization path (native claude/ provider)
Pre-existing bug, not introduced by issue #2260 changes.