fix(ui5-li): implement edit mode for keyboard navigation in list items (#13411)

Implements an edit mode for list items following the SAP Fiori
Keyboard Interaction spec (Intentional Edit Pattern, p86-87):

- **Navigation mode** (default): Tab/Shift+Tab forwards out of the
  list. Arrow keys navigate between items.
- **Edit mode** (toggled by F2 or F7): Tab flows through inner
  focusable elements within an item, then continues to the next
  item's elements, and exits the list after the last item.
  Shift+Tab flows backward symmetrically. Arrow Up/Down transfers
  focus to the same-index element in adjacent items.

The delete button in Delete selection mode is now keyboard
accessible — reachable via edit mode Tab flow without requiring
the Delete key shortcut.

Fixes #13220

Author: kgogov

packages/fiori/src/UploadCollectionItem.ts

@@ -237,6 +237,7 @@ class UploadCollectionItem extends ListItem {
 	async onDetailClick() {
 		super.onDetailClick();
 		this._editing = true;
+		this._editMode = true;
 
 		await this._initInputField();
 	}
@@ -300,6 +301,7 @@ class UploadCollectionItem extends ListItem {
 		this.fireDecoratorEvent("rename");
 
 		this._editing = false;
+		this._editMode = false;
 		this._focus();
 	}
 
@@ -311,6 +313,7 @@ class UploadCollectionItem extends ListItem {
 
 	async _onRenameCancel(e: KeyboardEvent | UI5CustomEvent<Button, "click">) {
 		this._editing = false;
+		this._editMode = false;
 
 		if (isEscape(e as KeyboardEvent)) {
 			await renderFinished();
@@ -326,6 +329,31 @@ class UploadCollectionItem extends ListItem {
 		}
 	}
 
+	_handleTabNext(e: KeyboardEvent) {
+		if (this._editMode) {
+			return super._handleTabNext(e);
+		}
+
+		if (this.shouldForwardTabAfter()) {
+			if (!this.fireDecoratorEvent("forward-after")) {
+				e.preventDefault();
+			}
+		}
+	}
+
+	_handleTabPrevious(e: KeyboardEvent) {
+		if (this._editMode) {
+			return super._handleTabPrevious(e);
+		}
+
+		const target = e.target as HTMLElement;
+		if (this.shouldForwardTabBefore(target)) {
+			if (!this.fireDecoratorEvent("forward-before")) {
+				e.preventDefault();
+			}
+		}
+	}
+
 	_focus() {
 		this.fireDecoratorEvent("focus-requested");
 	}