Adapt dbskill for Codex and add product metadata

[78460655]

Summary

This PR adapts dbskill for Codex usage and adds lightweight product metadata for a better in-app skill experience.

What changed

Codex compatibility

• adapt skill flows from Claude-oriented assumptions to Codex-friendly behavior
• rework dbs router so it routes and hands off with the first question instead of relying on implicit execution
• rewrite chatroom-austrian to avoid default multi-agent dependency
• rewrite dbskill-upgrade for Codex / Windows usage, including .codex/skills and .agents/skills
• normalize internal references toward $dbs-* style skill invocation

Product polish

• add agents/openai.yaml for all 9 skills
• add lightweight SVG icons for all 9 skills
• add display_name, short_description, default_prompt, and brand_color
• keep the changes low-token by avoiding large new instruction blocks in SKILL.md

Files changed

• modified 9 existing SKILL.md files
• added 9 agents/openai.yaml files
• added 9 assets/icon.svg files

Notes

• this PR does not include find-skills, since it is not part of the upstream dbskill repository
• validation was run against all adapted skills with the Codex skill validator

Validation

• validated all 9 skills with quick_validate.py
• confirmed the adapted package works from both .agents/skills and .codex/skills