feat: Universal Agent API Bridge & Modular Skill Engine Overhaul

- Add Gitea/Vikunja API sync scripts to eliminate prompt-pollution.
- Move submodules to .agent/vendor for proper CLI encapsulation.
- Implement extract_skills.js to dynamically flatten 19 active skills.
- Translate CLI skill descriptions to Korean.
- Mask .env.agent in .gitignore ensuring true Zero-Pollution secure template.

.agent/skills/.gitignore

@@ -0,0 +1,6 @@
+# Auto-generated by extract_skills.js
+*
+!.gitignore
+!ui-ux-pro-max/
+!browser_use/
+!mini-swe/