feat(omo-senpi): mirror ulw mutation skills

[realsigridjin]

Summary

• Mirror the eight requested packages/omo-senpi ULW mutation-test files into the native Senpi repository.
• Adapt the two copied test entrypoints to Senpi's existing Vitest and Node URL-path conventions so the native static gate remains green.
• No native runtime registration is introduced; this is the requested source mirror.

Validation

• npm run check passes.
• Direct execution of the copied OMO fixture tests confirms their remaining dependency on the unmirrored OMO plugin/shared-skill tree (6 pass, 7 fixture-dependent failures); the native CI does not register this mirror as a workspace package.

Scope

The PR intentionally changes only the eight requested packages/omo-senpi files.

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Summary by cubic

Mirrors the ULW mutation skills into @oh-my-opencode/omo-senpi and adds tests and scripts to keep them in sync. Adapts test entrypoints for vitest and Node URL paths; no runtime registration is added.

• New Features
  • Added skills docs: skills/ulw-mutation-test/, skills/ulw-loop/ (with references/full-workflow.md) and AGENTS.md.
  • Added plugin/scripts/sync-skills.mjs and QA script scripts/qa/ulw-prompts-e2e.mjs.
  • Added tests to verify skill sync and contract: src/components/ulw-loop/mutation-skill-contract.test.ts, src/skills-sync.test.ts.

^{Written for commit 2cf3e8e. Summary will update on new commits.}