Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

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This section details on the original issue you should resolve

<issue_title>Agent skill for creating new skills</issue_title>
<issue_description>We should follow many of the principles in the skills-modification skill, but there's a few other important ideas:

• before creating a new skill, check one doesn't already exist
• make sure to add cross-references to the new skill in other possibly-relevant skills, especially if it might be seen as a "subskill".

Came up in #1691 </issue_description>

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