fix(ci): add submodules checkout to coverage job (#85)

The coverage job was failing because the stackone-ai-node submodule
was not being checked out. The MCP mock server tests require this
submodule to be present for bun install to succeed.

Changes:
- Add submodules: true to coverage job checkout step (matching ci job)
- Add automatic submodule initialisation in flake.nix shellHook

This ensures submodules are available both in CI and local development.

Author: ryoppippi

.github/workflows/ci.yaml

@@ -73,6 +73,8 @@ jobs:
     steps:
       - name: Checkout repository
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          submodules: true
 
       - name: Setup Nix
         uses: ./.github/actions/setup-nix

flake.nix

@@ -108,6 +108,12 @@
             shellHook = ''
               echo "StackOne AI Python SDK development environment"
 
+              # Initialize git submodules if not already done
+              if [ -f .gitmodules ] && [ ! -f vendor/stackone-ai-node/package.json ]; then
+                echo "📦 Initializing git submodules..."
+                git submodule update --init --recursive
+              fi
+
               # Install Python dependencies only if .venv is missing or uv.lock is newer
               if [ ! -d .venv ] || [ uv.lock -nt .venv ]; then
                 echo "📦 Installing Python dependencies..."