feat(slice3): listRFCs accepts facet selections, returns {items,facets} (§22.4a)

frontend/src/api.js

@@ -203,11 +203,27 @@ export async function createProject({ projectId, name, type, visibility, content
 // §22.4 (Plan B) / §22 S2: per-collection serving. With a projectId + a
 // collectionId, read the collection-scoped routes; with only a projectId, the
 // project default-collection compat path; with neither, the unscoped path.
-export async function listRFCs(projectId, collectionId) {
-  if (projectId && collectionId) {
-    return jsonOrThrow(await fetch(`/api/projects/${projectId}/collections/${collectionId}/rfcs`))
+// §22.4a SLICE-3: faceted catalog. `opts.selections` is { field: string[] }
+// (each non-empty array becomes repeated query params, OR within the field);
+// `opts.malformed` toggles the malformed-only filter. Returns the full payload
+// { items, facets } — callers read both. With no selections it behaves as the
+// pre-SLICE-3 list (and a no-fields collection returns facets: {}). Facets are
+// served only on the project/collection-scoped paths, not the unscoped one.
+export async function listRFCs(projectId, collectionId, opts = {}) {
+  const { selections = {}, malformed = false } = opts
+  const qs = new URLSearchParams()
+  for (const [field, values] of Object.entries(selections)) {
+    for (const v of values) qs.append(field, v)
   }
-  const url = projectId ? `/api/projects/${projectId}/rfcs` : '/api/rfcs'
+  if (malformed) qs.set('malformed', 'true')
+  const query = qs.toString()
+  let base
+  if (projectId && collectionId) {
+    base = `/api/projects/${projectId}/collections/${collectionId}/rfcs`
+  } else {
+    base = projectId ? `/api/projects/${projectId}/rfcs` : '/api/rfcs'
+  }
+  const url = query ? `${base}?${query}` : base
   return jsonOrThrow(await fetch(url))
 }