fix(composer): lone typing group uses the full row width instead of truncating at the strip cap

- BotActivityBar.tsx: apply the typing slot's max-w-64 cap only when the
  group shares the strip with working-agent pills. The cap exists so a
  long "X, Y, and N more are typing" label can't inflate the strip's
  scroll extent alongside pills, but it was unconditional — as the
  strip's LONE item a two-name label ("Alpha Debug and Beta Debug are
  typing...") got cut off at 256px even with the row mostly empty. The
  lone item already shrinks with the container (min-w-0 through the
  slot chain), so it now consumes the row's free width and only
  ellipsizes when the container is genuinely narrow.
- channels.spec.ts: add "lone typing group uses the full row width"
  e2e regression — three typers push the label past the old cap, then
  asserts no truncation at full width (scrollWidth <= clientWidth) and
  graceful ellipsizing without scroll fades at a 200px row. Verified
  the test fails against the old unconditional cap.

Co-authored-by: Taylor Ho <taylorkmho@gmail.com>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

desktop/src/features/channels/ui/BotActivityBar.tsx

@@ -775,10 +775,16 @@ export function BotActivityComposerAction({
                   {() => (
                     <div
                       className={cn(
-                        // Cap like the pills (which use max-w-50 each) so a
-                        // long "X, Y, and N more are typing" label truncates
-                        // instead of inflating the scroll extent.
-                        "flex h-7 min-w-0 max-w-64 items-center",
+                        "flex h-7 min-w-0 items-center",
+                        // Only when sharing the strip with pills does the
+                        // group need a width cap (like the pills' max-w-50
+                        // each) so a long "X, Y, and N more are typing" label
+                        // truncates instead of inflating the scroll extent.
+                        // As the strip's lone item it shrinks with the
+                        // container instead (min-w-0 through the slot chain),
+                        // so a cap would only cut the label off in a row that
+                        // has room to spare.
+                        orderedAgents.length > 0 && "max-w-64",
                         // Composer-edge alignment when the typing group leads
                         // the strip (no pills): 0.75rem/1rem composer padding
                         // + 1px border. Mirrors the standalone row's old

desktop/tests/e2e/channels.spec.ts

@@ -3109,6 +3109,52 @@ test("typing indicator shows avatars and maintains stable name order", async ({
   ).toContainText("alice and bob are typing");
 });
 
+test("lone typing group uses the full row width instead of truncating at the strip cap", async ({
+  page,
+}) => {
+  await page.goto("/");
+
+  await page.getByTestId("channel-random").click();
+  await expect(page.getByTestId("chat-title")).toHaveText("random");
+  await waitForMockLiveSubscription(page, "random", KIND_TYPING_INDICATOR);
+
+  // Three typers push the label past the strip's shared-slot cap (max-w-64,
+  // 256px): with no pills the typing group is the strip's LONE item and must
+  // consume the row's free width instead of cutting the label off mid-name.
+  for (const identity of [
+    TEST_IDENTITIES.alice,
+    TEST_IDENTITIES.bob,
+    TEST_IDENTITIES.charlie,
+  ]) {
+    await page.evaluate((pubkey) => {
+      window.__BUZZ_E2E_EMIT_MOCK_TYPING__?.({
+        channelName: "random",
+        pubkey,
+      });
+    }, identity.pubkey);
+  }
+
+  const label = page.getByTestId("message-typing-indicator-label");
+  await expect(label).toContainText("alice, bob, and charlie are typing");
+
+  // No truncation with room to spare: the label's content fits its box.
+  await expect
+    .poll(() => label.evaluate((el) => el.scrollWidth - el.clientWidth))
+    .toBeLessThanOrEqual(0);
+
+  // Genuinely narrow, the lone group still shrinks with the container and
+  // ellipsizes (rather than overflowing into scroll under an edge fade).
+  await page
+    .getByTestId("channel-composer-activity-row")
+    .evaluate((element) => {
+      element.style.width = "200px";
+    });
+  await expect
+    .poll(() => label.evaluate((el) => el.scrollWidth - el.clientWidth))
+    .toBeGreaterThan(0);
+  await expect(page.getByTestId("bot-activity-strip-fade-end")).toHaveCount(0);
+});
+
 test("sidebar shows unread indicator for newly active channels", async ({
   page,
 }) => {