[Bug]: Global skills in domain subdirectories are not discovered

[nguyenngothuong]

Bug Description

Global skills organised with a domain/category subfolder are silently ignored by OpenWork.

OpenWork expects skills at:

~/.config/opencode/skills/<skill-name>/SKILL.md

But the OpenCode CLI convention (and many community setups) uses a domain-grouped layout:

~/.config/opencode/skills/<domain>/<skill-name>/SKILL.md

Steps to Reproduce

1. Organise global skills in domain subfolders:

   ~/.config/opencode/skills/
   ├── automation/
   │   └── my-skill/SKILL.md
   └── web-development/
       └── my-other-skill/SKILL.md
   

2. Open any workspace in OpenWork
3. Check the Skills panel

Expected: Both skills appear in the list
Actual: Skills panel is empty — skills are not discovered

Root Cause

Both gather_skills() in packages/desktop/src-tauri/src/commands/skills.rs and listSkillsInDir() in packages/server/src/skills.ts only scan one level deep (<root>/<name>/SKILL.md) and skip directories that don't directly contain SKILL.md.

Fix

When a top-level entry inside a skill root does not contain SKILL.md, treat it as a domain/category folder and scan its subdirectories for <name>/SKILL.md.
This is fully backwards-compatible — the flat layout still works as before.