docs(dates): record list-rows-omit-raw-provenance decision near render

Elicit asked that the "raw provenance shown on detail, not in list rows"
choice be captured as a product decision rather than a payload accident.
Add a code comment at the list-row DocumentDate render explaining
showRaw={false} and the intentional metaDateRaw omission from
DocumentListItem.

Refs #666

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/lib/document/DocumentRow.svelte

@@ -164,6 +164,10 @@ function safeTagColor(color: string | null | undefined): string {
 				<!-- Mobile-only metadata -->
 				<div class="mt-3 grid grid-cols-2 gap-x-4 gap-y-1 font-sans text-xs text-ink-2 sm:hidden">
 					<div>
+						<!-- Product decision (#666): raw provenance (meta_date_raw) is shown on the
+						     document DETAIL page, never in list/search rows — list rows surface only the
+						     honest label to keep scan-rows compact. showRaw={false} enforces this; the
+						     DocumentListItem payload also intentionally omits metaDateRaw. -->
 						{#if doc.documentDate}
 							<DocumentDate
 								iso={doc.documentDate}