ci: lowercase workflow names (#3)

Renames the top-level `name:` field on both workflows so the Actions
pane uses lowercase, coder-friendly naming:
- `_ci.yml`: `CI` → `ci`
- `opentofu.yml`: `OpenTofu` → `opentofu`

Job- and step-level names (`OpenTofu Plan`, `OpenTofu Apply`) are
unchanged — they are display labels within a run, not the workflow
listing.

🤖 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/_ci.yml

@@ -1,4 +1,4 @@
-name: CI
+name: ci
 
 on:
   pull_request:

.github/workflows/opentofu.yml

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