feat: add custom agents and quick-flow workflows, remove tech-spec track

Major Changes:
- Add sample custom agents demonstrating installable agent system
  - commit-poet: Generates semantic commit messages (BMAD Method repo sample)
  - toolsmith: Development tooling expert with knowledge base covering bundlers, deployment, docs, installers, modules, and tests (BMAD Method repo sample)
  - Both agents demonstrate custom agent architecture and are installable to projects via BMAD installer system
  - Include comprehensive installation guides and sidecar knowledge bases

- Add bmad-quick-flow methodology for rapid development
  - create-tech-spec: Direct technical specification workflow
  - quick-dev: Flexible execution workflow supporting both tech-spec-driven and direct instruction development
  - quick-flow-solo-dev (Barry): 1 man show agent specialized in bmad-quick-flow methodology
  - Comprehensive documentation for quick-flow approach and solo development

- Remove deprecated tech-spec workflow track
  - Delete entire tech-spec workflow directory and templates
  - Remove quick-spec-flow.md documentation (replaced by quick-flow docs)
  - Clean up unused epic and story templates

- Fix custom agent installation across IDE installers
  - Repair antigravity and multiple IDE installers to properly support custom agents
  - Enable custom agent installation via quick installer, agent installer, regular installer, and special agent installer
  - All installation methods now accessible via npx with full documentation

Infrastructure:
- Update BMM module configurations and team setups
- Modify workflow status paths to support quick-flow integration
- Reorganize documentation with new agent and workflow guides
- Add custom/ directory for user customizations
- Update platform codes and installer configurations

src/modules/bmb/docs/agent-menu-patterns.md

@@ -115,7 +115,7 @@ menu:
   - trigger: create-brief
     exec: '{project-root}/{bmad_folder}/core/tasks/create-doc.xml'
     tmpl: '{project-root}/{bmad_folder}/bmm/templates/brief.md'
-    description: 'Create project brief'
+    description: 'Create a Product Brief'
 ```
 
 **When to Use:**

src/modules/bmb/docs/module-agent-architecture.md

@@ -125,7 +125,7 @@ menu:
   - trigger: create-brief
     exec: '{project-root}/{bmad_folder}/core/tasks/create-doc.xml'
     tmpl: '{project-root}/{bmad_folder}/bmm/templates/brief.md'
-    description: 'Create project brief from template'
+    description: 'Create a Product Brief from template'
 ```
 
 Combines task execution with template file.

src/modules/bmb/workflows/create-agent/installation-guide.md

@@ -25,8 +25,8 @@ npx bmad-method agent-install --source ./my-agent.agent.yaml --destination ./my-
 
 ## Batch Install
 
-1. Copy agent YAML to `.bmad/custom/src/agents/`
-2. Run installer and select "Compile Agents"
+1. Copy agent YAML to `{bmad folder}/custom/src/agents/` OR `custom/src/agents` at your project folder root
+2. Run `npx bmad-method install` and select `Compile Agents` or `Quick Update`
 
 ## What Happens