refactor(frontend): the near-duplicate report rules shared via dup-report.css — KnowledgeView and SnippetListView carried identical scoped copies (#2903, milestone 299 step 5, part 2)

KnowledgeView's own comment asked for this promotion once a second view grew the
panel. The sheet carries .dup-panel / .dup-empty,.dup-head / .dup-group /
.dup-members / .dup-member(+:hover) / .dup-score; each view keeps only its
extras (.dup-claimed, .dup-action).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/SnippetListView.vue

@@ -517,6 +517,7 @@ function usageTitle(s: SnippetListItem): string {
   </main>
 </template>
 
+<style src="@/assets/dup-report.css" />
 <style scoped>
 .page-header {
   display: flex;
@@ -757,59 +758,6 @@ function usageTitle(s: SnippetListItem): string {
   color: var(--fs-text-tertiary);
 }
 
-/* Near-duplicate report */
-.dup-panel {
-  margin-bottom: 1.25rem;
-  padding: 0.85rem 1rem;
-  border: 1px solid var(--fs-border-color);
-  border-radius: 8px;
-  background: var(--fs-surface-hover);
-}
-
-.dup-empty,
-.dup-head {
-  margin: 0 0 0.5rem;
-  font-size: 0.85rem;
-  color: var(--fs-text-tertiary);
-}
-
-.dup-empty {
-  margin-bottom: 0;
-}
-
-.dup-group {
-  display: flex;
-  align-items: center;
-  gap: 0.75rem;
-  flex-wrap: wrap;
-  padding: 0.5rem 0;
-  border-top: 1px solid var(--fs-border-color);
-}
-
-.dup-members {
-  display: flex;
-  gap: 0.4rem;
-  flex-wrap: wrap;
-  flex: 1 1 20rem;
-  min-width: 0;
-}
-
-.dup-member {
-  font-size: 0.8rem;
-  padding: 0.1rem 0.45rem;
-  border-radius: 4px;
-  background: color-mix(in srgb, var(--fs-text-tertiary) 12%, transparent);
-  /* Long snippet names must not push the row into a horizontal scroll. */
-  overflow-wrap: anywhere;
-}
-
-.dup-score {
-  font-size: 0.75rem;
-  color: var(--fs-text-tertiary);
-  font-variant-numeric: tabular-nums;
-  white-space: nowrap;
-}
-
 .dup-action {
   white-space: nowrap;
 }