ci: lowercase workflow name (#7)

Renames the workflow's top-level `name:` from `OpenTofu` to `opentofu`
so the Actions pane uses lowercase, coder-friendly naming.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: xnoto

.github/workflows/opentofu.yml

@@ -1,4 +1,4 @@
-name: OpenTofu
+name: opentofu
 
 on:
   pull_request: