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>

package.json

@@ -48,7 +48,7 @@
     "url": "git+https://github.com/bmadcode/BMAD-METHOD.git"
   },
   "engines": {
-    "node": ">=14.0.0"
+    "node": ">=20.0.0"
   },
   "devDependencies": {
     "husky": "^9.1.7",
@@ -69,7 +69,7 @@
     ".roomodes": [
       "node tools/yaml-format.js"
     ],
-    ".bmad-core/**/*.yml": [
+    "bmad-core/**/*.yml": [
       "node tools/yaml-format.js"
     ],
     ".github/**/*.yml": [