feat: Extract BMGD module and implement workflow vendoring

This commit extracts game development functionality from BMM into a standalone
BMGD (BMad Game Development) module and implements workflow vendoring to enable
module independence.

BMGD Module Creation:
- Moved agents: game-designer, game-dev, game-architect from BMM to BMGD
- Moved team config: team-gamedev
- Created new Game Dev Scrum Master agent using workflow vendoring pattern
- Reorganized workflows into industry-standard game dev phases:
  * Phase 1 (Preproduction): brainstorm-game, game-brief
  * Phase 2 (Design): gdd, narrative
  * Phase 3 (Technical): game-architecture
  * Phase 4 (Production): vendored from BMM workflows
- Updated all module metadata and config_source references

Workflow Vendoring Feature:
- Enables modules to copy workflows from other modules during installation
- Build-time process that updates config_source in vendored workflows
- New agent YAML attribute: workflow-install (build-time metadata)
- Final compiled agents use workflow-install value for workflow attribute
- Implementation in module manager: vendorCrossModuleWorkflows()
- Allows standalone module installation without forced dependencies

Technical Changes:
- tools/cli/lib/yaml-xml-builder.js: Use workflow-install for workflow attribute
- tools/cli/installers/lib/modules/manager.js: Add vendoring functions
- tools/schema/agent.js: Add workflow-install to menu item schema
- Updated 3 documentation files with workflow vendoring details

BMM Workflow Updates:
- workflow-status/init: Added game detection checkpoint
- workflow-status/paths/game-design.yaml: Redirect to BMGD module
- prd/instructions.md: Route game projects to BMGD
- research/instructions-market.md: Reference BMGD for game development

Documentation:
- Created comprehensive BMGD module README
- Added workflow vendoring documentation
- Updated BMB agent creation and module creation guides

src/modules/bmm/workflows/workflow-status/init/instructions.md

@@ -317,6 +317,56 @@ Your choice [1/2/3]:</ask>
 - Default to "software" if not clearly a game
   </action>
 
+<check if="project_type == game">
+  <output>
+  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+🎮 **GAME DEVELOPMENT DETECTED**
+
+Game development workflows are now part of the **BMad Game Development (BMGD)** module.
+
+The BMM module is designed for software development. For game development, you'll need
+the BMGD module which provides specialized game development workflows and agents.
+
+**Would you like to:**
+a) Install BMGD module now (recommended for game projects)
+b) Continue with BMM workflows (for software projects only)
+
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+</output>
+
+<ask>Your choice [a/b]:</ask>
+
+  <check if="choice == a">
+    <output>
+    Please run the following command to install the BMGD module:
+
+    ```bash
+    bmad install bmgd
+    ```
+
+    After installation, you can start your game development workflow with the Game Designer agent.
+
+    This workflow-init will now exit. Re-run it after installing BMGD.
+    </output>
+    <action>Exit workflow with success status</action>
+
+  </check>
+
+  <check if="choice == b">
+    <output>
+    ⚠️ **Warning:** BMM workflows are optimized for software development, not game development.
+
+    You may encounter mismatched terminology and workflows. Consider installing BMGD for
+    a better game development experience.
+
+    Continuing with software development workflows...
+    </output>
+    <action>Set project_type = "software" (override game detection)</action>
+
+  </check>
+</check>
+
 <template-output>user_description</template-output>
 <template-output>field_type</template-output>
 <template-output>project_type</template-output>