ci: skip build on CI-only file changes

Add paths-ignore for .gitea/** so build.yml doesn't waste runner time
when only workflow files are modified.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build.yml

@@ -7,6 +7,8 @@ on:
       - 'feat/*'
     tags:
       - 'v*'
+    paths-ignore:
+      - '.gitea/**'
   workflow_dispatch:
 
 env: