Show observers as a full-width list on mobile (#122)

src/features/observers/ObserverPage.tsx

@@ -80,7 +80,7 @@ export function ObserverPage({ wsManager }: { wsManager: WsManager }) {
         </span>}
     />
     <div className="relative flex min-h-0 min-w-0 flex-1">
-      <div className="flex min-h-0 w-full shrink-0 flex-col p-4 md:w-[260px] md:pr-0">
+      <div className="flex min-h-0 w-full shrink-0 flex-col md:w-[260px] md:p-4 md:pr-0">
         <ObserverSidebar observers={observers} filtered={Boolean(search || status || type || broker || scope)} isPending={directory.isPending} isError={directory.isError}
           onRetry={() => void directory.refetch()} range={range} selectedId={id} onSelect={select} />
       </div>

src/features/observers/ObserverSidebar.tsx

@@ -4,7 +4,6 @@ import { useTranslation } from "react-i18next";
 import { getTopObservers } from "../../api/client";
 import { useRegion } from "../../hooks/useRegion";
 import { formatCount } from "../../lib/formatters";
-import { Card } from "../stats/cards";
 import { Segmented } from "../stats/Segmented";
 import { RANGE_MS, type StatsRange } from "../stats/types";
 import { observerName as nameOf } from "./observer-filter";
@@ -36,17 +35,18 @@ export function ObserverSidebar({ observers, filtered, isPending, isError, onRet
   }, [observers, sort, counts]);
 
   return (
-    <Card
-      title={t("tabs.Observers")}
-      right={<Segmented size="sm" ariaLabel={t("observerPage.sort")} value={sort} onChange={(v) => setSort(v as Sort)}
-        options={[{ value: "activity", label: t("observerPage.sortActivity") }, { value: "name", label: t("observerPage.sortName") }]} />}
-      className="flex min-h-0 w-full flex-col"
-    >
+    // a card at md+, an edge-to-edge list like the Nodes tab below it
+    <div className="flex min-h-0 w-full flex-col bg-bg-base md:rounded-lg md:border md:border-border md:bg-bg-surface md:p-3.5">
+      <div className="flex shrink-0 items-center justify-between gap-2 border-b border-border-subtle px-4 py-2 md:mb-2.5 md:border-0 md:p-0">
+        <div className="font-mono text-[11px] font-semibold uppercase tracking-wider text-text-normal">{t("tabs.Observers")}</div>
+        <Segmented size="sm" ariaLabel={t("observerPage.sort")} value={sort} onChange={(v) => setSort(v as Sort)}
+          options={[{ value: "activity", label: t("observerPage.sortActivity") }, { value: "name", label: t("observerPage.sortName") }]} />
+      </div>
       {isPending ? <div className="py-6 text-center font-mono text-[11px] text-text-dim">{t("common.loading")}</div>
         : isError ? <button type="button" onClick={onRetry} className="py-6 text-center font-mono text-[11px] text-danger">{t("common.loadFailed")} · {t("observerPage.retry")}</button>
         : rows.length === 0 ? <div className="py-6 text-center font-mono text-[11px] text-text-dim">{t(filtered ? "observerPage.noMatches" : "observerPage.none")}</div>
         : (
-          <div role="listbox" aria-label={t("tabs.Observers")} className="-mx-1 flex min-h-0 flex-col gap-0.5 overflow-y-auto px-1">
+          <div role="listbox" aria-label={t("tabs.Observers")} className="flex min-h-0 flex-col overflow-y-auto md:-mx-1 md:gap-0.5 md:px-1">
             {rows.map((o) => {
               const active = o.id === selectedId;
               const count = counts.get(o.id);
@@ -57,14 +57,14 @@ export function ObserverSidebar({ observers, filtered, isPending, isError, onRet
                   role="option"
                   aria-selected={active}
                   onClick={() => onSelect(o.id)}
-                  className={`relative shrink-0 overflow-hidden rounded border-l-2 px-2.5 py-1.5 text-left transition-colors ${
+                  className={`relative shrink-0 overflow-hidden border-b border-l-2 border-b-border-subtle px-4 py-3 text-left md:rounded md:border-b-0 md:px-2.5 md:py-1.5 transition-colors ${
                     active ? "border-primary bg-primary/10" : "border-transparent hover:bg-text-normal/3"
                   }`}
                 >
-                  {count != null && <div className="absolute inset-y-0 left-0 bg-secondary/15" style={{ width: `${(count / max) * 100}%` }} aria-hidden />}
+                  {count != null && <div className="absolute inset-y-0 left-0 bg-secondary/8 md:bg-secondary/15" style={{ width: `${(count / max) * 100}%` }} aria-hidden />}
                   <div className="relative flex items-center gap-2">
                     <span aria-hidden className={`h-1.5 w-1.5 shrink-0 rounded-full ${deriveObserverStatus(o) === "online" ? "bg-green" : "bg-text-dim/30"}`} />
-                    <span className={`min-w-0 flex-1 truncate font-mono text-[12px] ${active ? "text-text-bright" : "text-text-normal"}`}>{nameOf(o)}</span>
+                    <span className={`min-w-0 flex-1 truncate font-mono text-[13px] md:text-[12px] ${active ? "text-text-bright" : "text-text-normal"}`}>{nameOf(o)}</span>
                     <span className="shrink-0 font-mono text-[11px] tabular-nums text-text-muted">{count != null ? formatCount(count) : "—"}</span>
                   </div>
                 </button>
@@ -72,6 +72,6 @@ export function ObserverSidebar({ observers, filtered, isPending, isError, onRet
             })}
           </div>
         )}
-    </Card>
+    </div>
   );
 }