fix: create ~/.gemini directory before CLI invocation to prevent ENOENT

Gemini CLI 0.33.0 writes a user-level project registry at
~/.gemini/projects.json during cleanup. The atomic write fails with
ENOENT if ~/.gemini/ doesn't exist. Add mkdir -p before the first
gemini command to ensure the directory is present.

Author: michalszelagsonos

action.yml

@@ -275,6 +275,7 @@ runs:
           npm run bundle
           npm install --silent --no-audit --prefer-offline --global .
         fi
+        mkdir -p "${HOME}/.gemini"
         echo "Verifying installation:"
         if command -v gemini >/dev/null 2>&1; then
           gemini --version || echo "Gemini CLI installed successfully (version command not available)"