Node 20, installer improvements, agent improvements and Expansion Pack for game dev (#232)

* feat: add expansion pack installation system with game dev and infrastructure expansion packs

- Added expansion pack discovery and installation to BMAD installer
- Supports interactive and CLI installation of expansion packs
- Expansion pack files install to destination root (.bmad-core)
- Added game development expansion pack (.bmad-2d-phaser-game-dev)
  - Game designer, developer, and scrum master agents
  - Game-specific templates, tasks, workflows, and guidelines
  - Specialized for Phaser 3 + TypeScript development
- Added infrastructure devops expansion pack (.bmad-infrastructure-devops)
  - Platform engineering agent and infrastructure templates
- Expansion pack agents automatically integrate with IDE rules
- Added list:expansions command and --expansion-packs CLI option

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

* alpha expansion packs and installer update to support installing expansion packs optionally

* node20

---------

Co-authored-by: Brian Madison <brianmadison@Brians-MacBook-Pro.local>
Co-authored-by: Claude <noreply@anthropic.com>

bmad-core/agent-teams/team-fullstack.yml

@@ -0,0 +1,18 @@
+bundle:
+  name: Team Fullstack
+  icon: 🚀
+  description: Comprehensive full-stack development team capable of handling both greenfield  application development and brownfield enhancement projects. This team combines  strategic planning, user experience design, and holistic system architecture  to deliver complete solutions from concept to deployment. Specializes in  full-stack applications, SaaS platforms, enterprise apps, feature additions,  refactoring, and system modernization.
+agents:
+  - bmad-orchestrator
+  - analyst
+  - pm
+  - ux-expert
+  - architect
+  - po
+workflows:
+  - brownfield-fullstack
+  - brownfield-service
+  - brownfield-ui
+  - greenfield-fullstack
+  - greenfield-service
+  - greenfield-ui