Studio Playwright: snooze update banner before sending (#6576)

* Studio Playwright: snooze update banner before sending

The llama.cpp update banner is a fixed bottom-right toast (z-9998). When an
update is available it overlaps the composer's Send button and its subtree
intercepts the click, so send_and_wait times out (flaky; surfaces on the
Windows studio UI smoke, passes otherwise). Snooze the banner if it is
showing before each send, then wait for it to detach.

* Also snooze the web update banner before sending

The web update banner (web-update-banner, z-9999) is a fixed bottom-right
toast like the llama.cpp one and can overlap the Send button too. Loop over
both banners and snooze whichever is showing.

tests/studio/playwright_chat_ui.py

@@ -569,6 +569,21 @@ with sync_playwright() as p:
         #    this at temp 0), and the old non-empty predicate got stuck
         #    on such bubbles.
         bubbles_before = _bubble_count()
+        # The llama.cpp and web update banners are fixed bottom-right toasts
+        # (z-9998 / z-9999) that can overlap the composer's Send button and
+        # intercept the click. Snooze whichever is showing before sending.
+        for prefix in ("llama", "web"):
+            snooze_btn = page.locator(f'[data-testid="{prefix}-update-snooze-button"]')
+            if snooze_btn.count():
+                try:
+                    snooze_btn.first.click(timeout = 2_000)
+                    page.wait_for_selector(
+                        f'[data-testid="{prefix}-update-banner"]',
+                        state = "detached",
+                        timeout = 5_000,
+                    )
+                except Exception:
+                    pass
         composer.click()
         composer.fill(prompt)
         page.locator('button[aria-label="Send message"]').click()