Update CI workflow refs and context-menu tweak definitions

[jacksyrm]

Questions

• Did you test your changes or double-check that they work?
• Did you read and follow the Atlas Contribution Guidelines?

Describe your pull request

• bump/pin workflow action versions and lock the sxsc checkout to a specific ref in CI
• move trusted-installer merge context-menu entries from HKCR to explicit HKLM\Software\Classes paths
• adjust old-context-menu restore tweak execution path to improve reliability under playbook execution