pr factory/issue 144 codex support

[Favot]

• feat: add Codex integration output
• fix: drop generated Codex AGENTS output

What does this PR do?

Agent Information (if adding/modifying an agent)

• Agent Name:
• Category:
• Specialty:

Checklist

• Follows the agent template structure from CONTRIBUTING.md
• Includes YAML frontmatter with name, description, color
• Has concrete code/template examples (for new agents)
• Tested in real scenarios
• Proofread and formatted correctly

[msitarzewski]

Hey — heads up, we just merged #186 which refactors how convert.sh handles single-file outputs (Aider, Windsurf). Previously write_single_file_outputs() wrote all formats unconditionally; now each format has its own if block gated on --tool.

When you rebase (you'll have README conflicts from recent merges too), your Codex block should slot in cleanly as a third if following the same pattern:

if [[ "$tool" == "all" || "$tool" == "codex" ]]; then
  mkdir -p "$OUT_DIR/codex"
  cp "$CODEX_TMP" "$OUT_DIR/codex/AGENTS.md"
  info "Wrote integrations/codex/AGENTS.md"
fi

Thanks for the solid implementation — looking forward to merging this once it's rebased.