Extract disableElement/enableElement to shared module

Stimulus controllers were reaching into Turbo.StreamElement.prototype
to call disableElement/enableElement — tight coupling to Turbo internals.

Extract both functions to app/javascript/element_helpers.js and import
from there in application.js (which still assigns them to the Turbo
prototype for server-driven Turbo Stream actions), details_controller,
and readout_unit_controller.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/javascript/application.js

@@ -2,6 +2,7 @@
 // https://github.com/rails/importmap-rails
 import "@hotwired/turbo-rails"
 import "controllers"
+import { disableElement, enableElement } from "element_helpers"
 
 
 /* Hide page before loaded for testing purposes */
@@ -12,23 +13,13 @@ document.addEventListener('turbo:load', showPage)
 
 
 /* Turbo stream actions */
-Turbo.StreamElement.prototype.disableElement = function(element) {
-    element.setAttribute("disabled", "disabled")
-    element.setAttribute("aria-disabled", "true")
-    element.setAttribute("tabindex", "-1")
-}
+Turbo.StreamElement.prototype.disableElement = disableElement
+Turbo.StreamElement.prototype.enableElement = enableElement
 Turbo.StreamActions.disable = function() {
-  this.targetElements.forEach((e) => { this.disableElement(e) })
-}
-
-Turbo.StreamElement.prototype.enableElement = function(element) {
-    element.removeAttribute("disabled")
-    element.removeAttribute("aria-disabled")
-    // Assume 'tabindex' is not used explicitly, so removing it is safe
-    element.removeAttribute("tabindex")
+  this.targetElements.forEach(disableElement)
 }
 Turbo.StreamActions.enable = function() {
-  this.targetElements.forEach((e) => { this.enableElement(e) })
+  this.targetElements.forEach(enableElement)
 }
 
 /* TODO: change to visibility = collapse to avoid width change? */

app/javascript/controllers/details_controller.js

@@ -1,4 +1,5 @@
 import { Controller } from "@hotwired/stimulus"
+import { disableElement, enableElement } from "element_helpers"
 
 export default class extends Controller {
   static targets = ["countLabel", "submitButton", "list"]
@@ -18,10 +19,10 @@ export default class extends Controller {
     const count = this.element.querySelectorAll('input:checked:not([disabled])').length
     if (count > 0) {
       this.countLabelTarget.textContent = count + ' selected'
-      Turbo.StreamElement.prototype.enableElement(this.submitButtonTarget)
+      enableElement(this.submitButtonTarget)
     } else {
       this.countLabelTarget.textContent = this.countLabelTarget.dataset.prompt
-      Turbo.StreamElement.prototype.disableElement(this.submitButtonTarget)
+      disableElement(this.submitButtonTarget)
     }
   }
 

app/javascript/controllers/readout_unit_controller.js

@@ -1,13 +1,14 @@
 import { Controller } from "@hotwired/stimulus"
+import { disableElement, enableElement } from "element_helpers"
 
 export default class extends Controller {
   static targets = ["select", "button"]
 
   unitChanged() {
     if (this.selectTarget.value && this.selectTarget.value !== this.selectTarget.dataset.defaultUnitId) {
-      Turbo.StreamElement.prototype.enableElement(this.buttonTarget)
+      enableElement(this.buttonTarget)
     } else {
-      Turbo.StreamElement.prototype.disableElement(this.buttonTarget)
+      disableElement(this.buttonTarget)
     }
   }
 

app/javascript/element_helpers.js

@@ -0,0 +1,11 @@
+export function disableElement(element) {
+  element.setAttribute("disabled", "disabled")
+  element.setAttribute("aria-disabled", "true")
+  element.setAttribute("tabindex", "-1")
+}
+
+export function enableElement(element) {
+  element.removeAttribute("disabled")
+  element.removeAttribute("aria-disabled")
+  element.removeAttribute("tabindex")
+}