feat: implement recursive agent discovery and compilation

- Module agents now discovered recursively at any depth in agents folder
- .agent.yaml files are compiled to .md format during module installation
- Custom agents also support subdirectory structure
- Agents maintain their directory structure when installed
- YAML files are skipped during file copying as they're compiled separately
- Added compileModuleAgents method to handle YAML-to-MD compilation
- Updated discoverAgents to recursively search for .agent.yaml files
- Agents in subdirectories are properly placed in _cfg/agents with relative paths

This fixes issue where agents like cbt-coach were not being compiled
and were only copied as YAML files.

tools/cli/installers/lib/core/installer.js

@@ -2532,8 +2532,10 @@ If AgentVibes party mode is enabled, immediately trigger TTS with agent's voice:
             agentType = parts.slice(-2).join('-'); // Take last 2 parts as type
           }
 
-          // Create target directory
-          const agentTargetDir = path.join(customAgentsDir, finalAgentName);
+          // Create target directory - use relative path if agent is in a subdirectory
+          const agentTargetDir = agent.relativePath
+            ? path.join(customAgentsDir, agent.relativePath)
+            : path.join(customAgentsDir, finalAgentName);
           await fs.ensureDir(agentTargetDir);
 
           // Calculate paths