feat(explore/tags): return focus to the tag input after every action

Explore is a rapid walk-and-tag surface, so focus must keep returning to the tag
input with no extra click (operator-asked 2026-06-26). Two gaps closed:

- Navigation hardening: refocus on every focused-image change (neighbour click,
  breadcrumb, Random image, seed) now runs nextTick → requestAnimationFrame, so
  it lands AFTER the post-navigation re-render/paint instead of being stolen
  back by the neighbour-grid re-render.
- All tag actions refocus, in both Explore and the modal: tag add (existing/new)
  and remove now hand focus back like accept-suggestion already did; and the
  rename + fandom-assignment dialogs refocus on @after-leave (fires after
  Vuetify's own focus-return to the activator, so ours wins).

TagAutocomplete's mobile guard is preserved throughout (no soft-keyboard pop on
touch). Modal behaviour gains the same stickier focus — consistent, low-risk.

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

frontend/src/views/ExploreView.vue

@@ -130,14 +130,18 @@ const seeding = ref(false)
 const seedError = ref(null)
 const tagPanelRef = ref(null)
 
-// Auto-focus the tag input whenever the focused image changes (seed + every
-// walk) so tagging needs no extra click — the whole point of the workspace
-// (operator-asked 2026-06-26). Reuses TagPanel/TagAutocomplete's focus, which
-// keeps its own mobile guard (no soft-keyboard pop on touch).
-watch(
-  () => store.currentImageId,
-  (id) => { if (id != null) nextTick(() => tagPanelRef.value?.focusTagInput?.()) },
-)
+// Auto-focus the tag input after any action so tagging needs no extra click —
+// the whole point of the workspace (operator-asked 2026-06-26). nextTick waits
+// for the post-navigation re-render, then rAF lands the focus AFTER paint so a
+// neighbour/breadcrumb click that re-renders the grid can't steal it back.
+// Reuses TagPanel/TagAutocomplete's focus, which keeps its mobile guard (no
+// soft-keyboard pop on touch).
+function refocusTag () {
+  nextTick(() => requestAnimationFrame(() => tagPanelRef.value?.focusTagInput?.()))
+}
+// Every focused-image change (seed + every walk: neighbour click, breadcrumb,
+// Random image).
+watch(() => store.currentImageId, (id) => { if (id != null) refocusTag() })
 
 // The route is the source of truth. With an anchor, walk it; without one (the
 // bare /explore nav entry) seed a RANDOM image so the tab kick-starts a rabbit