chore: date the branch-named action pin comments

[kim-em]

This PR changes the trailing comments on action pins taken from a branch, such as # main, to say when the SHA was taken, such as # main as of 2026-09-28. A SHA pin no longer follows the branch, so the bare branch name read as if it did.

🤖 Prepared with Claude Code

[github-actions]

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[jstoobysmith]

Approved - will merge now