Suspense boundary

<section class="stage"><div class="heading">SUSPENSE <span class="hint">one slow boundary</span></div><div class="cards"><div class="tile ready"><b>PROFILE</b><span>Ready</span></div><div class="tile slow"><b>PICKS</b><span class="fallback">Loading ▬▬</span><span class="content">3 results</span></div><div class="tile ready"><b>FEED</b><span>Ready</span></div></div><div class="caption">Siblings stay visible while one region waits</div></section>

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