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

tools/cli/installers/lib/ide/codex.js

@@ -354,7 +354,7 @@ class CodexSetup extends BaseIdeSetup {
    * @returns {Object|null} Info about created command
    */
   async installCustomAgentLauncher(projectDir, agentName, agentPath, metadata) {
-    const destDir = this.getCodexPromptDir();
+    const destDir = this.getCodexPromptDir(projectDir, 'project');
     await fs.ensureDir(destDir);
 
     const launcherContent = `---
@@ -379,7 +379,7 @@ You must fully embody this agent's persona and follow all activation instruction
     await fs.writeFile(launcherPath, launcherContent, 'utf8');
 
     return {
-      path: launcherPath,
+      path: path.relative(projectDir, launcherPath),
       command: `/${fileName.replace('.md', '')}`,
     };
   }