fix(fandom): match change-fandom modal focus + Enter to FandomPicker

The 'Fandom for <character>' dialog (FandomSetDialog) used plain autofocus and
had no Enter handling, so Enter re-opened the dropdown instead of submitting —
the same bug FandomPicker already fixed. Mirror that flow: parent v-dialogs
focus the field via @after-enter→focusSearch (reliable past the focus-trap);
capture-phase Enter Saves the changed selection instead of re-opening the menu;
Tab jumps to the new-fandom field; creating a fandom returns focus to the
dropdown so a single Enter saves it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/modal/FandomSetDialog.vue

@@ -3,20 +3,29 @@
     <v-card-title class="text-body-1">Fandom for “{{ tag.name }}”</v-card-title>
     <v-card-text>
       <template v-if="!collision">
+        <!-- Keyboard flow matches FandomPicker (operator-specified 2026-06-07):
+             focus lands here via the parent dialog's @after-enter → focusSearch
+             (autofocus is unreliable inside a v-dialog focus-trap); Tab moves to
+             the new-fandom field; a SECOND Enter (menu closed) accepts the choice
+             by Saving instead of re-opening the dropdown. -->
         <v-autocomplete
+          ref="fandomRef"
           v-model="selectedId"
+          v-model:menu="menuOpen"
           :items="store.fandomCache"
           :item-title="(f) => f.name" :item-value="(f) => f.id"
           label="Fandom" clearable density="compact"
-          autofocus
           :hint="selectedId == null
             ? 'No fandom — the character will be unassigned.' : ''"
           persistent-hint
+          @keydown.enter.capture="onSearchEnter"
+          @keydown.tab="onSearchTab"
         />
         <v-divider class="my-3" />
         <p class="text-caption mb-2">Or create a new fandom:</p>
         <div class="d-flex" style="gap: 8px;">
           <v-text-field
+            ref="newNameRef"
             v-model="newName" placeholder="New fandom name"
             density="compact" hide-details
             @keydown.enter.prevent="onCreate"
@@ -71,7 +80,7 @@
 </template>
 
 <script setup>
-import { onMounted, ref } from 'vue'
+import { nextTick, onMounted, ref } from 'vue'
 import { useTagStore } from '../../stores/tags.js'
 
 const props = defineProps({ tag: { type: Object, required: true } })
@@ -84,10 +93,25 @@ const newName = ref('')
 const busy = ref(false)
 const error = ref(null)
 const collision = ref(null)
+const menuOpen = ref(false)
+const fandomRef = ref(null)
+const newNameRef = ref(null)
 
 // Always refresh on open so the list reflects fandoms created elsewhere (#712).
 onMounted(() => store.loadFandoms())
 
+// Exposed so the parent dialog can focus the search field on @after-enter —
+// the reliable point to grab focus (the dialog transition + focus-trap are done).
+function focusSearch() {
+  nextTick(() => {
+    fandomRef.value?.focus?.()
+    // Keep the menu closed after a programmatic focus so the very next Enter
+    // accepts the value (Saves) instead of being swallowed as a menu interaction.
+    menuOpen.value = false
+  })
+}
+defineExpose({ focusSearch })
+
 async function onCreate() {
   const name = newName.value.trim()
   if (!name) return
@@ -97,6 +121,9 @@ async function onCreate() {
     const f = await store.createFandom(name)
     selectedId.value = f.id
     newName.value = ''
+    // The created fandom is now the selection; hand focus back to the dropdown
+    // so a single Enter saves it (matches FandomPicker's flow).
+    focusSearch()
   } catch (e) {
     error.value = e.message || String(e)
   } finally {
@@ -104,6 +131,29 @@ async function onCreate() {
   }
 }
 
+// Enter on the search field — bound in the CAPTURE phase so it runs BEFORE
+// Vuetify's own handler (which opens the menu on Enter). Menu open → let Vuetify
+// pick the highlighted item. Menu closed with a changed selection → Save and stop
+// the event so Vuetify never (re)opens the dropdown (the bug this fixes).
+function onSearchEnter(e) {
+  if (menuOpen.value) return
+  if (busy.value) return
+  if (selectedId.value !== (props.tag.fandom_id ?? null)) {
+    e.preventDefault()
+    e.stopPropagation()
+    onSave()
+  }
+}
+
+// Tab from the search field goes to the "new fandom" text field (operator-
+// specified). Shift+Tab keeps normal reverse traversal.
+function onSearchTab(e) {
+  if (e.shiftKey) return
+  e.preventDefault()
+  menuOpen.value = false
+  nextTick(() => newNameRef.value?.focus?.())
+}
+
 async function save(merge) {
   busy.value = true
   error.value = null

frontend/src/components/modal/TagPanel.vue

@@ -34,8 +34,12 @@
       />
     </v-dialog>
 
-    <v-dialog v-model="fandomDialog" max-width="460">
+    <v-dialog
+      v-model="fandomDialog" max-width="460"
+      @after-enter="fandomSetRef?.focusSearch?.()"
+    >
       <FandomSetDialog
+        ref="fandomSetRef"
         v-if="fandomTarget" :tag="fandomTarget"
         @updated="onFandomUpdated" @cancel="fandomDialog = false"
       />
@@ -98,6 +102,7 @@ async function onRenamed() {
 
 const fandomDialog = ref(false)
 const fandomTarget = ref(null)
+const fandomSetRef = ref(null)
 function openSetFandom(tag) {
   fandomTarget.value = tag
   fandomDialog.value = true

frontend/src/views/TagsView.vue

@@ -87,8 +87,12 @@
       @confirm="onDeleteTagConfirm"
     />
 
-    <v-dialog v-model="fandomDialogOpen" max-width="460">
+    <v-dialog
+      v-model="fandomDialogOpen" max-width="460"
+      @after-enter="fandomSetRef?.focusSearch?.()"
+    >
       <FandomSetDialog
+        ref="fandomSetRef"
         v-if="fandomTarget" :tag="fandomTarget"
         @updated="onFandomUpdated" @cancel="fandomDialogOpen = false"
       />
@@ -152,6 +156,7 @@ function openTag(tagId) {
 // Character fandom editing (dots-menu → FandomSetDialog).
 const fandomDialogOpen = ref(false)
 const fandomTarget = ref(null)
+const fandomSetRef = ref(null)
 function onSetFandom(card) {
   fandomTarget.value = card
   fandomDialogOpen.value = true