refactor: renombrar agents/specials → agents/_specials

Establece la convención de que directorios con prefijo _ en agents/
son del sistema (templates, specials), no agentes desplegables.

Cambios:
- Renombrar agents/specials/ → agents/_specials/
- Actualizar path en cmd/launcher/main.go (startOrchestrator)
- Documentar convención _ en CLAUDE.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/launcher/main.go

@@ -283,10 +283,10 @@ type orchHandle struct {
 	cfg          *config.SpecialConfig
 }
 
-// startOrchestrator scans agents/specials/orchestrator/config.yaml and
+// startOrchestrator scans agents/_specials/orchestrator/config.yaml and
 // initializes the orchestrator if found and enabled.
 func startOrchestrator(agentBus *bus.Bus, logger *slog.Logger) (*orchHandle, error) {
-	cfgPath := filepath.Join("agents", "specials", "orchestrator", "config.yaml")
+	cfgPath := filepath.Join("agents", "_specials", "orchestrator", "config.yaml")
 	if _, err := os.Stat(cfgPath); os.IsNotExist(err) {
 		return nil, err
 	}