fix(dialog, modal, sheet): preserve focus-trap extra containers across internal trap updates (#11548)

**Related Issue:** #11523 

## Summary

Internal calls to `updateFocusTrap` caused user-provided
`extraContainers` to be lost. This updates `useFocusTrap` to maintain
stateful focusable containers for subsequent updates.

Author: jcfranco

packages/calcite-components/src/components/dialog/dialog.tsx

@@ -291,7 +291,8 @@ export class Dialog extends LitElement implements OpenCloseComponent, LoadableCo
   async updateFocusTrapElements(
     extraContainers?: FocusTrapOptions["extraContainers"],
   ): Promise<void> {
-    this.focusTrap.updateContainerElements(extraContainers);
+    this.focusTrap.setExtraContainers(extraContainers);
+    this.focusTrap.updateContainerElements();
   }
 
   /** When defined, provides a condition to disable focus trapping. When `true`, prevents focus trapping. */

packages/calcite-components/src/components/modal/modal.tsx

@@ -253,7 +253,8 @@ export class Modal extends LitElement implements OpenCloseComponent, LoadableCom
   async updateFocusTrapElements(
     extraContainers?: FocusTrapOptions["extraContainers"],
   ): Promise<void> {
-    this.focusTrap.updateContainerElements(extraContainers);
+    this.focusTrap.setExtraContainers(extraContainers);
+    this.focusTrap.updateContainerElements();
   }
 
   // #endregion

packages/calcite-components/src/components/sheet/sheet.tsx

@@ -234,7 +234,8 @@ export class Sheet extends LitElement implements OpenCloseComponent, LoadableCom
   async updateFocusTrapElements(
     extraContainers?: FocusTrapOptions["extraContainers"],
   ): Promise<void> {
-    this.focusTrap.updateContainerElements(extraContainers);
+    this.focusTrap.setExtraContainers(extraContainers);
+    this.focusTrap.updateContainerElements();
   }
 
   // #endregion

packages/calcite-components/src/controllers/useFocusTrap.ts

@@ -24,11 +24,16 @@ export interface UseFocusTrap {
   overrideFocusTrapEl: (el: HTMLElement) => void;
 
   /**
-   * Updates focusable elements within the trap.
+   * Sets the extra containers to be used in the focus trap.
    *
    * @see https://github.com/focus-trap/focus-trap#trapupdatecontainerelements
    */
-  updateContainerElements: (extraContainers?: FocusTrapOptions["extraContainers"]) => void;
+  setExtraContainers: (extraContainers?: FocusTrapOptions["extraContainers"]) => void;
+
+  /**
+   * Updates focusable elements within the trap.
+   */
+  updateContainerElements: () => void;
 }
 
 interface UseFocusTrapOptions<T extends LitElement = LitElement> {
@@ -100,6 +105,7 @@ export const useFocusTrap = <T extends FocusTrapComponent>(
   return makeGenericController<UseFocusTrap, T>((component, controller) => {
     let focusTrap: FocusTrap;
     let focusTrapEl: HTMLElement;
+    let effectiveContainers: FocusTrapOptions["extraContainers"];
     const internalFocusTrapOptions = options.focusTrapOptions;
 
     controller.onConnected(() => {
@@ -123,11 +129,9 @@ export const useFocusTrap = <T extends FocusTrapComponent>(
             ...internalFocusTrapOptions,
             ...component.focusTrapOptions,
           };
+          effectiveContainers ||= getEffectiveContainerElements(targetEl, component);
 
-          focusTrap = createFocusTrap(
-            getEffectiveContainerElements(targetEl, component),
-            createFocusTrapOptions(targetEl, effectiveFocusTrapOptions),
-          );
+          focusTrap = createFocusTrap(effectiveContainers, createFocusTrapOptions(targetEl, effectiveFocusTrapOptions));
         }
 
         if (
@@ -146,9 +150,12 @@ export const useFocusTrap = <T extends FocusTrapComponent>(
 
         focusTrapEl = el;
       },
-      updateContainerElements: (extraContainers?: FocusTrapOptions["extraContainers"]) => {
+      setExtraContainers: (extraContainers?: FocusTrapOptions["extraContainers"]) => {
         const targetEl = focusTrapEl || component.el;
-        return focusTrap?.updateContainerElements(getEffectiveContainerElements(targetEl, component, extraContainers));
+        effectiveContainers = getEffectiveContainerElements(targetEl, component, extraContainers);
+      },
+      updateContainerElements: () => {
+        return focusTrap?.updateContainerElements(effectiveContainers);
       },
     };
   });