fix: revert load_skills default and enforce via prompts instead

Revert .default([]) on load_skills schema back to required, restore the runtime error for missing load_skills, and add explicit load_skills=[] to all task() examples in agent prompts that were missing it.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/agents/prometheus/plan-generation.ts

@@ -61,6 +61,7 @@ todoWrite([
 \`\`\`typescript
 task(
   subagent_type="metis",
+  load_skills=[],
   prompt=\`Review this planning session before I generate the work plan:
 
   **User's Goal**: {summarize what user wants}