JKToolKit.CodexSDK

Research and implement repo-specific parity updates between JKToolKit.CodexSDK and the vendored upstream Codex CLI in `external/codex`. Use when `UPSTREAM_CODEX_VERSION.json` or `external/codex` changes, when a user asks what changed in codex-cli since the last parity pass, or when you need to audit and fix drift in exec-mode, app-server DTOs/parsers, docs, tests, or generated schema interop.