fix(audit-g2): async race / state-leak across eight stores

Extracts gallery.js's hand-rolled inflightId pattern into a new
useInflightToken composable; adopts in every store that previously
had no guard against late-response overwrites or wrong-image URL
interpolation.

Two operator-impacting bugs the audit (workflow wf_bbe3fdb1-e62)
flagged:

- modal.removeTag rolled back the chip rail unconditionally even
  when only the secondary dismiss POST had failed — UI lied until
  refresh. And all tag-mutation URLs interpolated currentImageId
  AFTER an await, so a fast prev/next could route DELETE/POST to
  the wrong image. Both fixed: split try/catch (dismiss failure
  surfaces a warning, doesn't roll back the delete); imageId
  captured at call-time and used in URLs throughout.

- suggestions.accept dereferenced currentImageId after the awaited
  POST /api/tags, so the subsequent /suggestions/accept could
  apply A's chosen tag to image B AND push it to B's allowlist.
  Fixed by capturing imageId at click-time + inflight guard on
  load().

Same shape across artist / downloads / artistDirectory /
tagDirectory / posts stores: rapid filter/nav changes used to
interleave responses (last-writer-wins). Now the late response is
discarded and the most-recent request wins. Filter-change-during-
search no longer drops the second fetch because the loading flag
was still true from the first.

gallery.js's inflightId removed in favor of the shared composable
so the pattern stays consistent.

frontend/src/stores/artist.js

@@ -1,6 +1,7 @@
 import { defineStore } from 'pinia'
 import { ref, computed } from 'vue'
 import { useApi } from '../composables/useApi.js'
+import { useInflightToken } from '../composables/useInflightToken.js'
 import { usePostsStore } from './posts.js'
 
 const PAGE = 60
@@ -15,12 +16,17 @@ export const useArtistStore = defineStore('artist', () => {
   const error = ref(null)
   const notFound = ref(false)
   let started = false
+  // Rapid artist-to-artist navigation used to render the previous
+  // artist's overview/images briefly when the second load resolved
+  // after the third. Audit 2026-06-02.
+  const inflight = useInflightToken()
 
   async function load (slug) {
     // Cross-artist reset: clear this store AND the posts store so the new
     // artist doesn't briefly render with the previous artist's content
     // when the user is on the Posts tab. (Gallery tab uses this artist
     // store's own images list — cleared above.)
+    inflight.cancel()
     overview.value = null
     images.value = []
     nextCursor.value = null
@@ -29,14 +35,18 @@ export const useArtistStore = defineStore('artist', () => {
     error.value = null
     loading.value = true
     usePostsStore().$reset?.()
+    const t = inflight.claim()
     try {
-      overview.value = await api.get(`/api/artist/${encodeURIComponent(slug)}`)
+      const body = await api.get(`/api/artist/${encodeURIComponent(slug)}`)
+      if (!t.isCurrent()) return
+      overview.value = body
       await loadMoreImages(slug)
     } catch (e) {
+      if (!t.isCurrent()) return
       if (e.status === 404) notFound.value = true
       else error.value = e.message
     } finally {
-      loading.value = false
+      if (t.isCurrent()) loading.value = false
     }
   }
 
@@ -44,19 +54,22 @@ export const useArtistStore = defineStore('artist', () => {
     if (imagesLoading.value) return
     if (started && nextCursor.value === null) return
     imagesLoading.value = true
+    const t = inflight.claim()
     try {
       const params = { limit: PAGE }
       if (nextCursor.value) params.cursor = nextCursor.value
       const body = await api.get(
         `/api/artist/${encodeURIComponent(slug)}/images`, { params }
       )
+      if (!t.isCurrent()) return
       images.value.push(...body.images)
       nextCursor.value = body.next_cursor
       started = true
     } catch (e) {
+      if (!t.isCurrent()) return
       error.value = e.message
     } finally {
-      imagesLoading.value = false
+      if (t.isCurrent()) imagesLoading.value = false
     }
   }