fix: configure Git to use main as default branch in CI

This resolves integration test failures where tests expected 'main'
branch but Git was creating repositories with 'master' as default.

🤖 Generated with [opencode](https://opencode.ai)

Co-Authored-By: opencode <noreply@opencode.ai>

Author: tinmancoding

.github/workflows/ci.yml

@@ -20,6 +20,9 @@ jobs:
       with:
         enable-cache: true
 
+    - name: Configure Git to use main as default branch
+      run: git config --global init.defaultBranch main
+        
     - name: Lint check
       run: devbox run lint
 
@@ -28,10 +31,10 @@ jobs:
 
     - name: Unit tests
       run: devbox run test:unit
-      
+        
     - name: Build for integration tests
       run: devbox run build
-      
+        
     - name: Integration tests
       run: devbox run test:integration
 
@@ -54,8 +57,11 @@ jobs:
       with:
         enable-cache: true
 
+    - name: Configure Git to use main as default branch
+      run: git config --global init.defaultBranch main
+        
     - name: Build for integration tests
       run: devbox run build
-        
+      
     - name: Integration tests
       run: devbox run test:integration