fix(feed): drop the compact row's columns by the ROW's width, not the viewport

The viewport was the wrong signal: the nav rail and filter panel move the
row's width by ~430px between them, so at a 1280 window with both pinned
every column still qualified while the row had 762px for 766px of them —
the title squeezed back to nothing, the exact bug the breakpoints were
meant to fix. My own comment predicted it and I didn't follow it through.

VirtualFeed already measures the container for colCount, so it now passes
the item's real width down. Measured in the failing config: title -4 ->
359 with the date column standing down.

frontend/src/components/VideoCard.tsx

@@ -149,7 +149,7 @@ function resumePct(video: Video): number {
 // reading as a column. The flex row this replaces let a "36:36" and a "3:31:09" push the marker
 // beside them to different places, and pulled it left again whenever the duration was absent
 // (live/upcoming) — visible as a ragged edge down the page.
-function RowMetaCells({ video, className }: { video: Video; className?: string }) {
+function RowMetaCells({ video }: { video: Video }) {
   const { t } = useTranslation();
   // Icons, not the labelled chips the thumbnail uses: at a glance this is the least important thing
   // in the row, so it gets about a letter's worth of width. Icons rather than a coloured dot
@@ -168,12 +168,7 @@ function RowMetaCells({ video, className }: { video: Video; className?: string }
   // widen a slot and the title column silently pays for it. rem, not px, so the whole cell tracks
   // the text-size setting the same way its contents do.
   return (
-    <div
-      className={clsx(
-        "shrink-0 grid grid-cols-[4rem_1rem_1rem] gap-1 items-center text-sm text-muted",
-        className
-      )}
-    >
+    <div className="shrink-0 grid grid-cols-[4rem_1rem_1rem] gap-1 items-center text-sm text-muted">
       {/* Right-aligned: a duration is a number, so the digits line up on their own edge (30px for
           "1:52" up to 59px for an 11-hour stream — 4rem holds the longest). */}
       <span className="text-right tabular-nums">
@@ -327,9 +322,20 @@ function Thumb({
   );
 }
 
+// What the one-line row needs before each column earns its place, cumulative from the left:
+// actions (192) + a title worth reading (~120) + gaps + the row's padding, then each column plus
+// its gap. Driven by the ROW's measured width, never the viewport — see VirtualFeed's itemWidth.
+const ROW_FITS = {
+  channel: 490,
+  meta: 606,
+  views: 682,
+  published: 886,
+};
+
 function VideoCard({
   video,
   view,
+  width,
   onState,
   onResetState,
   onToggleSave,
@@ -338,6 +344,8 @@ function VideoCard({
 }: {
   video: Video;
   view: FeedView;
+  /** Measured width of this card/row, from VirtualFeed. 0 until the first measure. */
+  width: number;
   onState: (id: string, status: string) => void;
   onResetState?: (id: string) => void;
   onToggleSave: (id: string, saved: boolean) => void;
@@ -458,6 +466,7 @@ function VideoCard({
     // The title takes what's left, which is constant per container width — so it aligns too.
     if (noThumb) {
       const pct = resumePct(video);
+      const fits = (needs: number) => width === 0 || width >= needs;
       return (
         <div className={clsx(rowShell, "flex items-center gap-3 px-3 py-2", watched && "opacity-55")}>
           {/* Actions lead: this is where the eye already is (the title is the thing you read), so
@@ -465,20 +474,24 @@ function VideoCard({
           <div className="shrink-0 w-48">{actions}</div>
           {/* Everything else is shrink-0, so the title is the only thing that can give — which means
               once the fixed columns outgrow the row, it gives ALL of it and vanishes. Columns drop
-              from the right as space runs out, least important first: a title with no date beats a
-              date with no title. Breakpoints are the viewport, not this row, so they're rough — the
-              rail and filter panel move the row's width too — but they're pitched to keep the title
-              alive at the narrow end rather than to hold every column to the last pixel. */}
+              from the right as the row narrows, least important first: a title with no date beats a
+              date with no title. `width` is the ROW's own, so this holds whatever the rail and the
+              filter panel are doing. Until the first measure lands (width 0) show everything: the
+              row is off-screen for that frame anyway, and guessing narrow would flash. */}
           <div className="min-w-0 flex-1">{title}</div>
-          <div className="shrink-0 w-32 hidden sm:block">{channelButton}</div>
-          <RowMetaCells video={video} className="hidden md:grid" />
+          {fits(ROW_FITS.channel) && <div className="shrink-0 w-32">{channelButton}</div>}
+          {fits(ROW_FITS.meta) && <RowMetaCells video={video} />}
           {/* Right-aligned like the duration: it's a number, so the digits share an edge. 64px
               holds the widest bare form ("101.7K" at 48) in either language — dropping the word
               took this from 144 and handed the difference to the title. */}
-          <div className="shrink-0 w-16 text-sm text-muted text-right tabular-nums truncate hidden lg:block">
-            {viewsCell(false)}
-          </div>
-          <div className="shrink-0 w-48 text-sm text-muted truncate hidden xl:block">{published}</div>
+          {fits(ROW_FITS.views) && (
+            <div className="shrink-0 w-16 text-sm text-muted text-right tabular-nums truncate">
+              {viewsCell(false)}
+            </div>
+          )}
+          {fits(ROW_FITS.published) && (
+            <div className="shrink-0 w-48 text-sm text-muted truncate">{published}</div>
+          )}
           {/* Thumb draws this over the image; with no image it goes on the row itself. */}
           {pct > 0 && (
             <div className="absolute bottom-0 left-2 right-2 h-1 rounded-full bg-black/40">

frontend/src/components/VirtualFeed.tsx

@@ -86,6 +86,12 @@ export default function VirtualFeed({
   // Distance from the scroll element's content top to where this list starts (the
   // feed toolbar sits above it inside the same scroll area).
   const [scrollMargin, setScrollMargin] = useState(0);
+  // How wide ONE row/card actually renders. The one-line row drops columns as this shrinks, and it
+  // has to be the real width, not the viewport: the nav rail (56 slim / ~230 pinned) and the filter
+  // panel (~80 tab / ~256 pinned) move it by ~430px between them. A viewport breakpoint got this
+  // wrong — at 1280 with both pinned every column still showed while the row had 762px for 766px of
+  // them, which squeezed the title to nothing. This is measured here anyway, for colCount.
+  const [itemWidth, setItemWidth] = useState(0);
 
   useLayoutEffect(() => {
     if (listRef.current) setScrollEl(getScrollParent(listRef.current));
@@ -103,7 +109,13 @@ export default function VirtualFeed({
           scrollEl.scrollTop;
         setScrollMargin(m);
       }
-      setColCount(columnsFor(view, node.clientWidth));
+      const w = node.clientWidth;
+      const cols = columnsFor(view, w);
+      setColCount(cols);
+      const { minCol: min, maxCol: max } = FEED_VIEW_SPEC[view];
+      setItemWidth(
+        min == null ? Math.min(w, max ?? w) : Math.floor((w - GRID_GAP * (cols - 1)) / cols)
+      );
     };
     measure();
     const ro = new ResizeObserver(measure);
@@ -168,6 +180,7 @@ export default function VirtualFeed({
                   key={v.id}
                   video={v}
                   view={view}
+                  width={itemWidth}
                   onState={onState}
                   onToggleSave={onToggleSave}
                   onOpenChannel={onOpenChannel}