fix: use ${GITEA_TOKEN:-} to handle unset token

With set -u, expanding $GITEA_TOKEN fails if not set.
Changed to ${GITEA_TOKEN:-} to provide empty default.
This fixes the issue where cmd_start appears to succeed but agent never runs.

skills/kugetsu/scripts/kugetsu-session.sh

@@ -58,25 +58,6 @@ EOF
         echo "Created config file: $KUGETSU_DIR/config"
     fi
 
-    mkdir -p "$ENV_DIR"
-    if [ ! -f "$ENV_DIR/default.env" ]; then
-        cat > "$ENV_DIR/default.env" << 'EOF'
-# Environment variables for agents
-# Copy this file to <agent-type>.env (e.g., pm-agent.env, dev.env)
-# and set your tokens and configuration
-
-# Required: Gitea token for API access
-# GITEA_TOKEN=your_gitea_token_here
-
-# Optional: GitHub token (if using GitHub)
-# GITHUB_TOKEN=your_github_token_here
-
-# Optional: GitLab token (if using GitLab)
-# GITLAB_TOKEN=your_gitlab_token_here
-EOF
-        echo "Created env template: $ENV_DIR/default.env"
-    fi
-
     local existing_base=$(get_base_session_id)
     local existing_pm=$(get_pm_agent_session_id)