chore(web): icon layout switcher with radio semantics

Replace the layout Select with a lean 28px segmented control: Rows3 /
Columns2 / Columns3 / Infinity icons on a quiet muted track, only the
active option filled. Each option carries a tooltip with a label and an
honest description of the ceiling semantics ("up to N columns when the
width allows").

The control is a proper radiogroup — roving tabindex, arrow-key
movement, aria-checked — restoring the single-choice semantics the
Select used to provide. Options derive from ViewContext's canonical
value list, and one exhaustive record maps each value to its icon and
wording, so a future column option fails to compile until both exist.

The Compact mode row now stays visible in multi-column layouts, shown
as on and locked (multi-column always renders compact tiles); the
stored preference is untouched and resurfaces at a single column.

web/src/components/MemoDisplaySettingMenu.tsx

@@ -1,6 +1,7 @@
-import { Settings2Icon } from "lucide-react";
+import { Columns2Icon, Columns3Icon, InfinityIcon, type LucideIcon, Rows3Icon, Settings2Icon } from "lucide-react";
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
 import { Switch } from "@/components/ui/switch";
+import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
 import { MAX_COLUMNS_VALUES, type MemoMaxColumns, useView } from "@/contexts/ViewContext";
 import { cn } from "@/lib/utils";
 import { useTranslate } from "@/utils/i18n";
@@ -10,8 +11,15 @@ interface Props {
   className?: string;
 }
 
-// Derived from the context's canonical value list so the two can never drift; 0 renders as ∞.
-const MAX_COLUMNS_OPTIONS = MAX_COLUMNS_VALUES.map((value) => ({ value, label: value === 0 ? "∞" : String(value) }));
+// Keyed by the context's canonical value list, so adding a column option forces an icon and
+// wording here at compile time. The i18n param is deliberately named `n`, not `count` —
+// i18next would route `count` through plural-form lookup.
+const LAYOUT_OPTIONS: Record<MemoMaxColumns, { icon: LucideIcon; key: "layout-list" | "layout-columns" | "layout-auto" }> = {
+  1: { icon: Rows3Icon, key: "layout-list" },
+  2: { icon: Columns2Icon, key: "layout-columns" },
+  3: { icon: Columns3Icon, key: "layout-columns" },
+  0: { icon: InfinityIcon, key: "layout-auto" },
+};
 
 function MemoDisplaySettingMenu({ className }: Props) {
   const t = useTranslate();
@@ -28,6 +36,9 @@ function MemoDisplaySettingMenu({ className }: Props) {
     setMaxColumns,
   } = useView();
   const isApplying = orderByTimeAsc !== false || timeBasis !== "create_time" || compactMode || !linkPreview || maxColumns !== 1;
+  // Multi-column grids always render compact tiles, so the toggle is shown as on and locked
+  // there; it only becomes a real choice at a single column.
+  const compactLocked = maxColumns !== 1;
 
   return (
     <Popover>
@@ -37,20 +48,59 @@ function MemoDisplaySettingMenu({ className }: Props) {
       <PopoverContent align="end" alignOffset={-12} sideOffset={14}>
         <div className="flex flex-col gap-2 p-1">
           <div className="w-full flex flex-row justify-between items-center">
-            <span className="text-sm shrink-0 mr-3 text-foreground">{t("memo.columns")}</span>
-            {/* Radix only reports rendered item values, so no re-validation is needed here. */}
-            <Select value={String(maxColumns)} onValueChange={(value) => setMaxColumns(Number(value) as MemoMaxColumns)}>
-              <SelectTrigger size="sm" className="w-32">
-                <SelectValue />
-              </SelectTrigger>
-              <SelectContent>
-                {MAX_COLUMNS_OPTIONS.map((option) => (
-                  <SelectItem key={option.value} value={String(option.value)}>
-                    {option.label}
-                  </SelectItem>
-                ))}
-              </SelectContent>
-            </Select>
+            <span className="text-sm shrink-0 mr-3 text-foreground">{t("memo.layout")}</span>
+            {/* A quiet muted track (28px tall, borderless); only the active option carries the accent
+                fill. A radiogroup with roving tabindex, since the options are mutually exclusive. */}
+            <div
+              role="radiogroup"
+              aria-label={t("memo.layout")}
+              className="flex items-center gap-0.5 rounded-lg bg-muted/50 p-0.5"
+              onKeyDown={(event) => {
+                const delta =
+                  event.key === "ArrowRight" || event.key === "ArrowDown"
+                    ? 1
+                    : event.key === "ArrowLeft" || event.key === "ArrowUp"
+                      ? -1
+                      : 0;
+                if (delta === 0) return;
+                event.preventDefault();
+                const index = MAX_COLUMNS_VALUES.indexOf(maxColumns);
+                const next = MAX_COLUMNS_VALUES[(index + delta + MAX_COLUMNS_VALUES.length) % MAX_COLUMNS_VALUES.length];
+                setMaxColumns(next);
+                event.currentTarget.querySelector<HTMLButtonElement>(`[data-value="${next}"]`)?.focus();
+              }}
+            >
+              {MAX_COLUMNS_VALUES.map((value) => {
+                const { icon: Icon, key } = LAYOUT_OPTIONS[value];
+                const label = t(`memo.${key}`, { n: value });
+                const active = maxColumns === value;
+                return (
+                  <Tooltip key={value}>
+                    <TooltipTrigger asChild>
+                      <button
+                        type="button"
+                        role="radio"
+                        aria-checked={active}
+                        aria-label={label}
+                        tabIndex={active ? 0 : -1}
+                        data-value={value}
+                        onClick={() => setMaxColumns(value)}
+                        className={cn(
+                          "grid h-6 w-7 place-items-center rounded-md transition-colors",
+                          active ? "bg-accent text-accent-foreground" : "text-muted-foreground/70 hover:bg-accent/50 hover:text-foreground",
+                        )}
+                      >
+                        <Icon className="w-3.5 h-3.5" />
+                      </button>
+                    </TooltipTrigger>
+                    <TooltipContent>
+                      <p className="font-medium">{label}</p>
+                      <p className="text-primary-foreground/70">{t(`memo.${key}-description`, { n: value })}</p>
+                    </TooltipContent>
+                  </Tooltip>
+                );
+              })}
+            </div>
           </div>
           <div className="w-full flex flex-row justify-between items-center">
             <span className="text-sm shrink-0 mr-3 text-foreground">{t("memo.shown-time")}</span>
@@ -83,13 +133,12 @@ function MemoDisplaySettingMenu({ className }: Props) {
               </SelectContent>
             </Select>
           </div>
-          {/* Multi-column grids always render compact tiles, so the toggle only applies to a single column. */}
-          {maxColumns === 1 && (
           <div className="w-full flex flex-row justify-between items-center">
-              <span className="text-sm shrink-0 mr-3 text-foreground">{t("memo.compact-mode")}</span>
-              <Switch checked={compactMode} onCheckedChange={setCompactMode} />
+            <span className={cn("text-sm shrink-0 mr-3", compactLocked ? "text-muted-foreground" : "text-foreground")}>
+              {t("memo.compact-mode")}
+            </span>
+            <Switch checked={compactLocked || compactMode} onCheckedChange={setCompactMode} disabled={compactLocked} />
           </div>
-          )}
           <div className="w-full flex flex-row justify-between items-center">
             <span className="text-sm shrink-0 mr-3 text-foreground">{t("memo.link-preview")}</span>
             <Switch checked={linkPreview} onCheckedChange={setLinkPreview} />

web/src/locales/en.json

@@ -265,8 +265,14 @@
       "has-task-list": "hasTaskList",
       "label": "Filters"
     },
-    "columns": "Columns",
     "compact-mode": "Compact mode",
+    "layout": "Layout",
+    "layout-auto": "Auto",
+    "layout-auto-description": "As many columns as fit the screen",
+    "layout-columns": "{{n}} columns",
+    "layout-columns-description": "Up to {{n}} columns when the width allows",
+    "layout-list": "List",
+    "layout-list-description": "A single reading-width column",
     "link-preview": "Link preview",
     "links": "Links",
     "load-more": "Load more",