fix(bulk-upload): truncate long chip titles with tooltip in FileSwitcherStrip

Long filenames caused chips to overflow the strip. Added max-w-[8rem]
and truncate on the title span, plus a title attribute for full text
on hover.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/document/FileSwitcherStrip.svelte

@@ -101,7 +101,7 @@ $effect(() => {
 							].join(' ')}
 							>{i + 1}</span
 						>
-						{entry.title}
+						<span class="max-w-[8rem] truncate" title={entry.title}>{entry.title}</span>
 					</button>
 					<button
 						type="button"