Skill: Process Library (parent brief)

This skill is the main thread's playbook for the Analyze Video workflow step — processing the footage in a library that already exists. Use it whenever the user wants to:

• Analyze a newly created library (this is where create-library hands off after scaffolding).
• Return to an existing library and continue from wherever analysis left off.
• Add new footage to an existing library and analyze just the new clips.

It orchestrates the full transcribe-audio → contact sheets → summaries pipeline. The mechanics of each analysis step live in skills/analyze-video/SKILL.md; this skill calls into them.

Step 1 — Locate the library

You need an existing library to process. Confirm which one:

ruby lib/buttercut/library.rb <name> exists   # exits 0 if it does, 1 if not