fix(bootstrap-instance): generar content/_index.md (portada)

Sin la portada, zola build fallaba en toda instancia recién creada:
get_url no podía resolver @/_index.md desde section.html. Encontrado
al probar bootstrap-instance de extremo a extremo (zola build real,
no sólo validate --skip-zola) para sembrar el repo motor.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

internal/clusterlog/commands_bootstrap.go

@@ -85,6 +85,22 @@ func (a *App) runBootstrapInstance(args []string) error {
 func writeScaffold(root, productName, baseURL string) ([]string, error) {
 	created := []string{}
 
+	title := "Bitácora Operativa"
+	if strings.TrimSpace(productName) != "" {
+		title = productName
+	}
+
+	homeTmpl, err := scaffoldFS.ReadFile(scaffoldRoot + "/content/_index.md.tmpl")
+	if err != nil {
+		return nil, NewError(ExitInternal, "internal", "plantilla de portada faltante", err.Error())
+	}
+	homeContent := renderScaffoldTemplate(string(homeTmpl), map[string]string{"TITLE": title})
+	homePath := filepath.Join(root, "content", "_index.md")
+	if err := writeFileAtomic(homePath, []byte(homeContent), 0o644); err != nil {
+		return nil, NewError(ExitInternal, "internal", err.Error(), homePath)
+	}
+	created = append(created, homePath)
+
 	for _, section := range scaffoldSections {
 		src := scaffoldRoot + "/content/" + section + "/_index.md"
 		data, err := scaffoldFS.ReadFile(src)
@@ -102,10 +118,6 @@ func writeScaffold(root, productName, baseURL string) ([]string, error) {
 	if err != nil {
 		return nil, NewError(ExitInternal, "internal", "plantilla zola.toml faltante", err.Error())
 	}
-	title := "Bitácora Operativa"
-	if strings.TrimSpace(productName) != "" {
-		title = productName
-	}
 	zolaContent := renderScaffoldTemplate(string(zolaTmpl), map[string]string{
 		"BASE_URL":     baseURL,
 		"TITLE":        title,