Add Forgejo Actions CI workflow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.forgejo/workflows/ci.yaml

@@ -0,0 +1,22 @@
+name: Proto CI
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install buf
+        uses: bufbuild/buf-setup-action@v1
+
+      - name: Lint protos
+        run: buf lint
+
+      - name: Check breaking changes
+        if: github.event_name == 'pull_request'
+        run: buf breaking --against '.git#branch=main'