fix(frontend): restore readable model activity timeline

frontend/src/shell/ModelActivityPanel.tsx

@@ -8,10 +8,17 @@ import { Button } from "../components/ui/button";
 import { isNearBottom } from "./activityScroll";
 
 const VISIBLE_MODEL_ACTIVITY_KINDS: ReadonlySet<ActivityKind> = new Set([
+  "prompt",
   "thinking",
-  "status",
+  "assistant",
 ]);
 
+const ACTIVITY_LABELS: Readonly<Partial<Record<ActivityKind, string>>> = {
+  prompt: "Question",
+  thinking: "Reasoning",
+  assistant: "Response",
+};
+
 export function isVisibleModelActivity(entry: ActivityEntry): boolean {
   return VISIBLE_MODEL_ACTIVITY_KINDS.has(entry.kind);
 }
@@ -36,54 +43,14 @@ function MarkdownBody({ entry }: { entry: ActivityEntry }) {
   );
 }
 
-function ActivityBody({ entry }: { entry: ActivityEntry }) {
-  if (entry.kind === "assistant" || entry.kind === "thinking") {
-    return <MarkdownBody entry={entry} />;
-  }
-
-  if (entry.kind === "status") {
-    const tone =
-      entry.level === "error"
-        ? "text-destructive"
-        : entry.level === "warning"
-          ? "text-amber-600"
-          : "text-foreground";
-    return <p className={`whitespace-pre-wrap break-words text-sm leading-relaxed ${tone}`}>{entry.text}</p>;
-  }
-
-  if (entry.kind === "lifecycle") {
-    return <p className="whitespace-pre-wrap break-words text-sm leading-relaxed text-muted-foreground">{entry.text}</p>;
-  }
-
-  return <p className="whitespace-pre-wrap break-words text-sm leading-relaxed text-foreground">{entry.text}</p>;
-}
-
 function ActivityRow({ entry }: { entry: ActivityEntry }) {
   return (
-    <article className="border-b border-border/50 py-3 last:border-b-0">
-      <div className="mb-1.5 flex flex-wrap items-center gap-1.5 text-[0.65rem] font-semibold uppercase tracking-[0.08em] text-muted-foreground">
-        {entry.phase && <span>{entry.phase}</span>}
-        <span>{entry.kind}</span>
-        {entry.status && (
-          <span className={entry.status === "failed" ? "text-destructive" : undefined}>
-            {entry.status}
-          </span>
-        )}
-        {entry.level && (
-          <span
-            className={
-              entry.level === "error"
-                ? "text-destructive"
-                : entry.level === "warning"
-                  ? "text-amber-600"
-                  : undefined
-            }
-          >
-            {entry.level}
-          </span>
-        )}
+    <article className="border-b border-border/50 py-2 last:border-b-0">
+      <div className="mb-1 flex flex-wrap items-center gap-1 text-[0.65rem] font-semibold uppercase tracking-[0.08em] text-muted-foreground">
+        <span className="text-foreground/80">{ACTIVITY_LABELS[entry.kind]}</span>
+        {entry.phase && <span aria-label={`Phase ${entry.phase}`}>{entry.phase}</span>}
       </div>
-      <ActivityBody entry={entry} />
+      <MarkdownBody entry={entry} />
     </article>
   );
 }
@@ -104,7 +71,7 @@ export function ModelActivityPanel({ onClose }: { onClose: () => void }) {
 
   return (
     <aside className="flex w-2/5 shrink-0 flex-col border-r border-border bg-sidebar">
-      <div className="flex items-center justify-between border-b border-border/60 px-3 py-3">
+      <div className="flex items-center justify-between border-b border-border/60 px-3 py-2">
         <h2 className="font-heading text-sm font-semibold text-foreground">Model activity</h2>
         <Button size="icon-sm" variant="ghost" aria-label="Close model activity" onClick={onClose}>
           <X className="size-4" />