chore(ui): dedup last 3 jscpd clones → 0 (collapsed rail, video-card text block, subs column)

- CollapsedFilterRail: the byte-identical 31-line collapsed sidebar rail was in
  both Sidebar (feed) and PlexSidebar → one shared component.
- VideoCard: the title + channel-button + meta block was duplicated across the
  list-row and card layouts → a local `textBlock` element (only one layout branch
  renders, so reusing the element is safe).
- subsColumn<T>(t): the identical 'subscribers' DataTable column in Channels +
  ChannelDiscovery → a generic factory in channelColumns.tsx.

All behavior-neutral; jscpd now reports 0 clones (was 8 at Phase 0 baseline).
tsc + knip green.

frontend/src/components/Sidebar.tsx

@@ -5,7 +5,6 @@ import {
   Check,
   ChevronDown,
   ChevronLeft,
-  ChevronRight,
   Eye,
   EyeOff,
   GripVertical,
@@ -13,7 +12,6 @@ import {
   Pencil,
   RotateCcw,
   Share2,
-  SlidersHorizontal,
   User,
   X,
 } from "lucide-react";
@@ -44,6 +42,7 @@ import { useDebounced } from "../lib/useDebounced";
 import { Switch } from "./ui/form";
 import TagManager from "./TagManager";
 import SavedViewsWidget from "./SavedViewsWidget";
+import CollapsedFilterRail from "./CollapsedFilterRail";
 
 // Filter ids; display labels resolved at render time via t("sidebar.sort.<id>") etc.
 const SORT_IDS = [
@@ -477,30 +476,7 @@ export default function Sidebar({
   // Collapsed: a thin rail (mirroring the nav) — an expand control plus a filter icon that
   // carries the active-filter count so you can tell filters are on without opening it.
   if (collapsed) {
-    return (
-      <aside className="hidden md:flex w-[46px] shrink-0 flex-col items-center gap-2 border-r border-border bg-surface/40 py-3">
-        <button
-          onClick={onToggleCollapse}
-          title={t("sidebar.expandPanel")}
-          aria-label={t("sidebar.expandPanel")}
-          className="p-1 rounded-md text-muted hover:text-fg hover:bg-card transition"
-        >
-          <ChevronRight className="w-4 h-4" />
-        </button>
-        <button
-          onClick={onToggleCollapse}
-          title={t("sidebar.filters")}
-          className="relative p-2 rounded-lg text-muted hover:text-fg hover:bg-card transition"
-        >
-          <SlidersHorizontal className="w-5 h-5" />
-          {activeCount > 0 && (
-            <span className="absolute -top-1 -right-1 min-w-[16px] h-4 px-1 rounded-full bg-accent text-accent-fg text-[10px] font-bold leading-none grid place-items-center ring-2 ring-bg">
-              {activeCount > 9 ? "9+" : activeCount}
-            </span>
-          )}
-        </button>
-      </aside>
-    );
+    return <CollapsedFilterRail activeCount={activeCount} onToggleCollapse={onToggleCollapse} />;
   }
 
   return (