fix: use bash shell for CI test steps on all platforms

Force bash shell for test and coverage steps to avoid PowerShell
parameter parsing issues on Windows (`.out` being treated as separate arg).

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

.github/workflows/ci.yml

@@ -24,11 +24,13 @@ jobs:
         run: |
           cd codeagent-wrapper
           go test -v -cover -coverprofile=coverage.out ./...
+        shell: bash
 
       - name: Check coverage
         run: |
           cd codeagent-wrapper
           go tool cover -func=coverage.out | grep total | awk '{print $3}'
+        shell: bash
 
       - name: Upload coverage
         uses: codecov/codecov-action@v4