devx tests were validating infra, grm, sso-bridge, and Mattermost OIDC
workflow/skill files. This is an architecture violation — devx must not
be aware of other repos. Those repos consume devx, not the other way
round.
Tests now only validate devx's own workflows and skills.
Closes DEVX-160
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>