fix: sync marketplace.json to v2.0.0 and fix cx-history frontmatter

feat: add /cxx advanced mode, reasoning effort tiers, score threshold, and core path review

fix: portable script paths for marketplace and manual install

fix: hooks.json format - use object instead of array

refactor: restructure as marketplace with plugins/ subdirectory

feat: add plugin marketplace metadata for Claude Code installation

feat: subagent architecture with semantic review and auto-invoke

Initial commit: Codex Reviewer plugin for Claude Code