Address review feedback (P3): The User-Installed Skills block was duplicated verbatim in two if/else branches in both buildCategorySkillsDelegationGuide() and Atlas buildSkillsSection(). Extract shared formatCustomSkillsBlock() with configurable header level (#### vs **) so both builders reference a single source of truth.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Custom skills from .config/opencode/skills/ were visible in agent prompts but the model consistently ignored them when delegating via delegate_task(). The flat skill table made no distinction between built-in and user-installed skills, causing the model to default to built-in ones only.
- Separate skills into 'Built-in Skills' and 'User-Installed Skills (HIGH PRIORITY)' sections in buildCategorySkillsDelegationGuide()
- Add CRITICAL warning naming each custom skill explicitly
- Add priority note: 'When in doubt, INCLUDE rather than omit'
- Show source column (user/project) for custom skills
- Apply same separation in buildUltraworkSection()
- Add 10 unit tests covering all skill combination scenarios
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
