fix(ci): lowercase 'molecule-ai/' in cross-repo workflow refs

Gitea is case-sensitive on owner slugs; canonical is lowercase
`molecule-ai/...`. Mixed-case `Molecule-AI/...` refs fail-at-0s
when the runner tries to resolve the cross-repo workflow / checkout.

Same fix as molecule-controlplane#12. Mechanical case-correction;
no behavior change beyond making CI resolve again.

Refs: internal#46

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -2,4 +2,4 @@ name: CI
 on: [push, pull_request]
 jobs:
   validate:
-    uses: Molecule-AI/molecule-ci/.github/workflows/validate-plugin.yml@main
+    uses: molecule-ai/molecule-ci/.github/workflows/validate-plugin.yml@main