fix(exercises): autofocus RTE when answer/hint editor opens

Answer and hint fields now receive focus when their RTE opens (on
click or when a new answer/hint is added), matching the existing
behaviour of the question editor. Cursor is placed at the end of any
existing text so the user can type immediately.

Also fixes a pre-existing bug in HintsEditor desktop layout where
@open-editor was passing the undefined variable `answerIdx` instead
of `hintIdx`.

Fixes #5885

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

Author: akolson

contentcuration/contentcuration/frontend/channelEdit/components/AnswersEditor/AnswersEditor.vue

@@ -94,6 +94,7 @@
                         v-model="answer.answer"
                         class="editor"
                         :mode="isAnswerOpen(answerIdx) ? 'edit' : 'view'"
+                        :autofocus="isAnswerOpen(answerIdx)"
                         :imageProcessor="EditorImageProcessor"
                         @update="updateAnswerText($event, answerIdx)"
                         @minimize="emitClose"
@@ -164,6 +165,7 @@
                       v-model="answer.answer"
                       class="editor"
                       :mode="isAnswerOpen(answerIdx) ? 'edit' : 'view'"
+                      :autofocus="isAnswerOpen(answerIdx)"
                       :imageProcessor="EditorImageProcessor"
                       @update="updateAnswerText($event, answerIdx)"
                       @minimize="emitClose"

contentcuration/contentcuration/frontend/channelEdit/components/HintsEditor/HintsEditor.vue

@@ -51,6 +51,7 @@
                     <TipTapEditor
                       v-model="hint.hint"
                       :mode="isHintOpen(hintIdx) ? 'edit' : 'view'"
+                      :autofocus="isHintOpen(hintIdx)"
                       :image-processor="EditorImageProcessor"
                       @update="updateHintText($event, hintIdx)"
                       @minimize="emitClose"
@@ -79,10 +80,11 @@
                     <TipTapEditor
                       v-model="hint.hint"
                       :mode="isHintOpen(hintIdx) ? 'edit' : 'view'"
+                      :autofocus="isHintOpen(hintIdx)"
                       :image-processor="EditorImageProcessor"
                       @update="updateHintText($event, hintIdx)"
                       @minimize="emitClose"
-                      @open-editor="emitOpen(answerIdx)"
+                      @open-editor="emitOpen(hintIdx)"
                     />
                   </keep-alive>
                 </transition>

contentcuration/contentcuration/frontend/shared/views/TipTapEditor/TipTapEditor/TipTapEditor.vue

@@ -205,6 +205,11 @@
           if (editor.value && editor.value.isEditable !== (newMode === 'edit')) {
             editor.value.setEditable(newMode === 'edit');
           }
+          if (newMode === 'edit' && editor.value && props.autofocus) {
+            nextTick(() => {
+              editor.value.commands.focus('end');
+            });
+          }
         },
       );