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/bmb/workflows/create-agent/instructions.md

@@ -193,9 +193,23 @@ menu:
   - trigger: [emerging from conversation]
     workflow: [path based on capability]
     description: [user's words refined]
-```
+
+# For cross-module workflow references (advanced):
+
+- trigger: [another capability]
+  workflow: "{project-root}/bmad/SOURCE_MODULE/workflows/path/to/workflow.yaml"
+  workflow-install: "{project-root}/bmad/THIS_MODULE/workflows/vendored/path/workflow.yaml"
+  description: [description]
+
+`````
 </example>
 
+<note>**Workflow Vendoring (Advanced):**
+When an agent needs workflows from another module, use both `workflow` (source) and `workflow-install` (destination).
+During installation, the workflow will be copied and configured for this module, making it standalone.
+This is typically used when creating specialized modules that reuse common workflows with different configurations.
+</note>
+
 <template-output>agent_commands</template-output>
 </step>
 
@@ -298,14 +312,16 @@ menu: {{The capabilities built}}
 
 **Folder Structure:**
 
-```
+`````
+
 {{agent_filename}}-sidecar/
-├── memories.md         # Persistent memory
-├── instructions.md     # Private directives
-├── knowledge/         # Knowledge base
-│   └── README.md
-└── sessions/          # Session notes
-```
+├── memories.md # Persistent memory
+├── instructions.md # Private directives
+├── knowledge/ # Knowledge base
+│ └── README.md
+└── sessions/ # Session notes
+
+````
 
 **File: memories.md**
 
@@ -323,7 +339,7 @@ menu: {{The capabilities built}}
 ## Personal Notes
 
 <!-- My observations and insights -->
-```
+````
 
 **File: instructions.md**