Phoenix Docs Gap Audit

Find everything in the Phoenix repo that shipped recently without proper documentation. The output is a gap report — not release notes, not new docs. The gap report tells the user (or a follow-up skill) exactly what is missing, where it should live, and what the new content should say, grounded in real code.

This skill is deliberately thorough. Documentation gaps are expensive: users hit undocumented features blind, stale examples teach wrong APIs, and in-code docstrings go missing silently because nothing fails CI. A good audit reads the actual code, cross-references every doc surface, and produces a report a maintainer can act on without re-doing the investigation.

Scope — what counts as "documentation"

Phoenix has several doc surfaces. A feature can be fully released and still be undocumented on most of them. Audit all of these: