feat(base): add BaseViewDraft type and view-draft atom family

apps/client/src/features/base/atoms/view-draft-atom.ts

@@ -0,0 +1,22 @@
+import { atomFamily, atomWithStorage } from "jotai/utils";
+import { BaseViewDraft } from "@/features/base/types/base.types";
+
+export type ViewDraftKey = {
+  userId: string;
+  baseId: string;
+  viewId: string;
+};
+
+export const viewDraftStorageKey = (k: ViewDraftKey) =>
+  `docmost:base-view-draft:v1:${k.userId}:${k.baseId}:${k.viewId}`;
+
+// `atomWithStorage` handles JSON serialization, cross-tab sync via the
+// `storage` event, and lazy first-read out of the box. `atomFamily`'s
+// comparator ensures the same triple resolves to the same atom instance
+// across renders, so identity-equality cache hits in Jotai still work.
+export const viewDraftAtomFamily = atomFamily(
+  (k: ViewDraftKey) =>
+    atomWithStorage<BaseViewDraft | null>(viewDraftStorageKey(k), null),
+  (a, b) =>
+    a.userId === b.userId && a.baseId === b.baseId && a.viewId === b.viewId,
+);

apps/client/src/features/base/types/base.types.ts

@@ -299,3 +299,14 @@ export type UpdatePropertyResult = {
   // when the job finished migrating cells.
   jobId: string | null;
 };
+
+// Local-first draft of filter / sort tweaks for a single view, stored in
+// localStorage scoped to (userId, baseId, viewId). An absent `filter` or
+// `sorts` field means "inherit the baseline for that axis". See
+// `.claude/superpowers/specs/2026-04-20-base-view-draft-design.md`.
+export type BaseViewDraft = {
+  filter?: FilterGroup;
+  sorts?: ViewSortConfig[];
+  // ISO timestamp written on each put; diagnostic only, not read by logic.
+  updatedAt: string;
+};