chore(agents): Add scan all mode for security skill

[github-actions]

Note

The pull request "chore(agents): Add scan all mode for security skill" was created by @chargome but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

Adds a "scan all" mode to the security fix skill: /fix-security-vulnerability --all. Which will interactively iterate over all open security issues in this repo. The user is prompted for every issue for the action to take. Fixes will be carried out on separate branches, so they do not cross-pollute.

Did a quick trial and closed about 30 issues in 10 minutes.

[linear]

JS-1843