refactor(documents): split triggerSearch by zoom semantics (#385)

triggerSearch(zoomOverride?) made the call site read "depends on
whether the source event happened to include zoomFrom/zoomTo". Splits
into triggerSearchKeepZoom() and triggerSearchWithZoom(from, to) so
the contract is explicit at every call site. Closes Felix's review
nit.

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

frontend/src/routes/documents/+page.svelte

@@ -81,10 +81,23 @@ function buildSearchParams(filters: FilterSnapshot, targetPage?: number): Svelte
 }
 
 /**
- * Rebuilds the URL from the CURRENT local filter state. `page` is intentionally
+ * Rebuilds the URL from the CURRENT local filter state, preserving the zoom
- * not carried over — any filter change implicitly resets back to page 0.
+ * range carried in `data.zoom{From,To}`. `page` is intentionally not carried
+ * over — any filter change implicitly resets back to page 0.
  */
-function triggerSearch(zoomOverride?: { zoomFrom: string | null; zoomTo: string | null }) {
+function triggerSearchKeepZoom() {
+	navigateWithZoom(data.zoomFrom ?? null, data.zoomTo ?? null);
+}
+
+/**
+ * Rebuilds the URL from the CURRENT local filter state and replaces the zoom
+ * range with the provided values (or clears it if both are null).
+ */
+function triggerSearchWithZoom(zoomFrom: string | null, zoomTo: string | null) {
+	navigateWithZoom(zoomFrom, zoomTo);
+}
+
+function navigateWithZoom(zoomFrom: string | null, zoomTo: string | null) {
 	const params = buildSearchParams({
 		q,
 		from,
@@ -96,8 +109,8 @@ function triggerSearch(zoomOverride?: { zoomFrom: string | null; zoomTo: string
 		dir,
 		tagQ,
 		tagOp: tagOperator,
-		zoomFrom: zoomOverride ? zoomOverride.zoomFrom : data.zoomFrom,
+		zoomFrom,
-		zoomTo: zoomOverride ? zoomOverride.zoomTo : data.zoomTo
+		zoomTo
 	});
 	goto(`/documents?${params.toString()}`, { keepFocus: true, noScroll: true });
 }
@@ -130,12 +143,12 @@ function buildPageHref(targetPage: number): string {
 
 function handleTextSearch() {
 	clearTimeout(searchTimer);
-	searchTimer = setTimeout(() => triggerSearch(), 500);
+	searchTimer = setTimeout(() => triggerSearchKeepZoom(), 500);
 }
 
 function handleImmediateSearch() {
 	clearTimeout(searchTimer);
-	triggerSearch();
+	triggerSearchKeepZoom();
 }
 
 // Trigger search reactively when the tag list changes.
@@ -144,7 +157,7 @@ $effect(() => {
 	const cur = tagNames.map((t) => t.name).join(',');
 	if (cur !== prevTagStr) {
 		prevTagStr = cur;
-		triggerSearch();
+		triggerSearchKeepZoom();
 	}
 });
 
@@ -256,19 +269,13 @@ $effect(() => {
 				// Drag commits filter + zoom atomically (Graylog-style range selector).
 				// Single click and clear omit zoomFrom/zoomTo so existing zoom is preserved.
 				if ('zoomFrom' in event) {
-					triggerSearch({
+					triggerSearchWithZoom(event.zoomFrom ?? null, event.zoomTo ?? null);
-						zoomFrom: event.zoomFrom ?? null,
-						zoomTo: event.zoomTo ?? null
-					});
 				} else {
-					triggerSearch();
+					triggerSearchKeepZoom();
 				}
 			}}
 			onzoomchange={(event) => {
-				triggerSearch({
+				triggerSearchWithZoom(event?.zoomFrom ?? null, event?.zoomTo ?? null);
-					zoomFrom: event?.zoomFrom ?? null,
-					zoomTo: event?.zoomTo ?? null
-				});
 			}}
 		/>
 	</div>