skill-creator: Where do user_notes.md and metrics.json come from?

Skill creator has steps for consuming `user_notes.md` and `metrics.json`. However, there is nothing in the skill's workflow that generates these files. Where do they come from?

Read the skill creator workflow where `user_notes.md` and `metrics.json` are consumed. Trace whether the workflow or another documented entry point provides these files, then make their source or generation steps explicit so a user can follow the workflow without guessing.

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