test(tuning): query the window/last-week headers as column headers — #2495

getByText(/Plays/) matched my own new caption as well as the header, since
the caption explains which columns cover the window. Query by columnheader
role instead, which is what the assertion actually means.

Also reordered the caption: prepending the clarification turned it into a
run-on that opened mid-explanation before saying what the chart was.

web/src/routes/admin/tuning/+page.svelte

@@ -428,13 +428,12 @@
     <div>
       <h2 class="text-lg font-semibold">Weekly trends</h2>
       <p class="text-xs text-text-secondary">
-        <span class="font-medium">Skip and completion are the most recent week only</span> —
-        the number after the skip rate is that week's play count, so a rate off a
-        handful of plays reads as what it is. Plays and Taste hit cover the whole
-        window.
         Skip rate per surface over the last {trends?.weeks ?? 12} weeks (lower is better; all
         users aggregated, rates only). Dashed ticks mark tuning changes. Taste hit is the share
         of plays whose artist fits the current taste profile.
+        <span class="font-medium">The skip and completion columns show the most recent week
+        alone</span>, not the whole window — the figure after the skip rate is that week's
+        play count, so a rate drawn from a handful of listens reads as what it is.
       </p>
     </div>
     {#if trendsFailed}