fix(ci): skill docs may name the project files a workflow writes

[miguel-heygen]

Summary

The comment-citation gate reads markdown, so it grades skill docs. Skill workflow docs name files that the workflow writes into the user's project at run time (frame.md, STORYBOARD.md, SCRIPT.md, _role.md). Those files never exist in this repo, so every touched line naming one failed as "no such file in the repo".

This adds them as one named list in check-comment-citations.mjs. The exemption matches the bare name only: a repo path that merely ends in one of these names is still resolved and still fails when missing.

Why

#3951 fixes 35 broken skill-doc links. Its "Comments" check fails on 13 lines it rewrote, all bare frame.md, STORYBOARD.md or _role.md. Any skill-doc PR touching such a line hits the same false failure.

Test plan

• New case: a bare project-file name in a skill doc passes.
• New case: skills/demo/frame.md, a repo path ending in a project-file name, still fails with "no such file".
• Mutation: removing the PROJECT_FILES check fails the first case; matching on the basename instead of the bare name fails the second.
• The gate probe (scripts/gate-probes/broken-citation.md) is unchanged and still reports both of its dead citations.

Size

20 changed lines: one named list, one check, two tests. The whole fix is the exemption; nothing else in the gate changes.

[github-actions]

Edit accuracy: accurate 1216 (base branch 1216), smooth 1110 of those

The gate passes.
Smoothness is reported in the artifact, not gated. A case fails only if it fails 2 of 3 runs.

Quarantined, measured but not gated (1)

• seqnudge-none-pct-r0-nested-z100 (fixed by fix(studio): playhead keyframe edits keep their ease, undo names its edit and never waits on videos #4889): pass, passes