fix(ci): use docker runner label instead of ubuntu-latest

The Gitea Actions runner on meghsakha uses label "docker".

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -20,7 +20,7 @@ jobs:
   # ========================================
 
   go-lint:
-    runs-on: ubuntu-latest
+    runs-on: docker
     if: github.event_name == 'pull_request'
     container: golangci/golangci-lint:v1.55-alpine
     steps:
@@ -32,7 +32,7 @@ jobs:
           fi
 
   python-lint:
-    runs-on: ubuntu-latest
+    runs-on: docker
     if: github.event_name == 'pull_request'
     container: python:3.12-slim
     steps:
@@ -52,7 +52,7 @@ jobs:
           fi
 
   nodejs-lint:
-    runs-on: ubuntu-latest
+    runs-on: docker
     if: github.event_name == 'pull_request'
     container: node:20-alpine
     steps:
@@ -74,7 +74,7 @@ jobs:
   # ========================================
 
   test-go-school:
-    runs-on: ubuntu-latest
+    runs-on: docker
     container: golang:1.23-alpine
     env:
       CGO_ENABLED: "0"
@@ -93,7 +93,7 @@ jobs:
           echo "Coverage: $COVERAGE"
 
   test-python-klausur:
-    runs-on: ubuntu-latest
+    runs-on: docker
     container: python:3.12-slim
     env:
       CI: "true"
@@ -112,7 +112,7 @@ jobs:
           python -m pytest tests/ -v --tb=short
 
   test-python-agent-core:
-    runs-on: ubuntu-latest
+    runs-on: docker
     container: python:3.12-slim
     env:
       CI: "true"
@@ -133,7 +133,7 @@ jobs:
           python -m pytest tests/ -v --tb=short
 
   test-nodejs-website:
-    runs-on: ubuntu-latest
+    runs-on: docker
     container: node:20-alpine
     steps:
       - uses: actions/checkout@v4