fix(chat): drop misleading "<1s" from merged reasoning label when timing is unknown

Addresses the second AI review comment on #724. When no reasoning step reports
a duration, durationMs is undefined and the label previously read
"Thought for <1s · N steps" — "<1s" implies fast when it really means "no timing
data". Now label by step count alone ("N steps") in that case; the
"Thought for {total} · N steps" form is used only when at least one step
reported timing. Updates the pinned unit test to assert the new behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: blove

libs/chat/src/lib/compositions/chat/chat.component.spec.ts

@@ -733,13 +733,13 @@ describe('ChatComponent — reasoning runs (merged pill)', () => {
       expect(run.label).toBe('Thought for 2s · 2 steps');
     });
 
-    it('all durations undefined → durationMs undefined; label falls back to "<1s" (documents current behavior)', () => {
-      // Flagged by review: "<1s" reads as "fast" when it really means "no timing
-      // data". This pins the CURRENT behavior so any intentional change is visible.
+    it('all durations undefined → durationMs undefined; label drops the duration phrase ("N steps")', () => {
+      // Per review: "Thought for <1s" reads as "fast" when timing is actually
+      // unknown. With no step reporting a duration, label by step count alone.
       const a = api([user('u1'), reasoning('a1', 'first'), tool('t1'), reasoning('a2', 'second')]);
       const run = a.reasoningRun(1);
       expect(run.durationMs).toBeUndefined();
-      expect(run.label).toBe('Thought for <1s · 2 steps');
+      expect(run.label).toBe('2 steps');
     });
 
     it('mixed defined/undefined durations sum only the numeric ones', () => {

libs/chat/src/lib/compositions/chat/chat.component.ts

@@ -500,7 +500,8 @@ export class ChatComponent {
   /**
    * Aggregate the reasoning RUN starting at `index`: joins each step's
    * reasoning, sums durations, counts steps, and computes the streaming flag
-   * and the merged label ("Thought for {total} · {N} steps" when N > 1).
+   * and the merged label when N > 1 ("Thought for {total} · {N} steps", or
+   * just "{N} steps" when no step reported timing).
    */
   protected reasoningRun(index: number): {
     content: string;
@@ -523,9 +524,14 @@ export class ChatComponent {
     const durationMs = durations.length ? durations.reduce((a, b) => a + b, 0) : undefined;
     const last = steps[steps.length - 1];
     const streaming = last ? this.isReasoningStreaming(last.msg, last.idx) : false;
+    // Only claim a duration when at least one step reported timing. Otherwise
+    // "Thought for <1s" would read as "fast" when it really means "unknown", so
+    // drop the duration phrase and label by step count alone.
     const label =
       steps.length > 1
-        ? `Thought for ${formatDuration(durationMs ?? 0)} · ${steps.length} steps`
+        ? durationMs !== undefined
+          ? `Thought for ${formatDuration(durationMs)} · ${steps.length} steps`
+          : `${steps.length} steps`
         : undefined;
     return { content, durationMs, streaming, label };
   }