Share repository guidance across Codex and Claude Code

[rullopat]

Summary

• track AGENTS.md as the canonical cross-platform repository guidance
• make CLAUDE.md import AGENTS.md using Claude Code's supported @path syntax
• refresh Node/Vite requirements and add the shipped harness/enforcement/approval invariants
• update current documentation references to the canonical file

Verification

• git diff --check
• verified Claude Code @path imports against Anthropic's official memory documentation

Documentation-only change; no runtime or production behavior changes.