feat: add faceted table toolbars and multi-value filters

Consolidating document and template filtering into shared faceted
toolbars makes filtering easier to discover and use.
Supporting comma-separated query params enables multi-select filters
across UI, server queries, and E2E coverage.

packages/lib/utils/params.ts

@@ -1,8 +1,3 @@
-/**
- * From an unknown string, parse it into an integer array.
- *
- * Filter out unknown values.
- */
 export const parseToIntegerArray = (value: unknown): number[] => {
   if (typeof value !== 'string') {
     return [];
@@ -14,6 +9,30 @@ export const parseToIntegerArray = (value: unknown): number[] => {
     .filter((value) => !isNaN(value));
 };
 
+export const parseToStringArray = (value: unknown): string[] => {
+  if (Array.isArray(value)) {
+    return value.filter((item): item is string => typeof item === 'string');
+  }
+
+  if (typeof value !== 'string') {
+    return [];
+  }
+
+  return value
+    .split(',')
+    .map((item) => item.trim())
+    .filter(Boolean);
+};
+
+export const parseCommaSeparatedValues = (value: unknown): string[] | undefined => {
+  const parsed = parseToStringArray(value);
+  return parsed.length > 0 ? parsed : undefined;
+};
+
+export const toCommaSeparatedSearchParam = (values: string[]): string | undefined => {
+  return values.length > 0 ? values.join(',') : undefined;
+};
+
 type GetRootHrefOptions = {
   returnEmptyRootString?: boolean;
 };