feat(admin) : persist drafts and add constellation conditions

lib/editor/local-draft.ts

@@ -0,0 +1,39 @@
+export const LOCAL_DRAFT_SCHEMA_VERSION = 1;
+
+export interface LocalDraftEnvelope<Draft> {
+  schemaVersion: typeof LOCAL_DRAFT_SCHEMA_VERSION;
+  serverVersion: number;
+  updatedAt: string;
+  draft: Draft;
+}
+
+export function adminDraftKey(guideId: string, section: string): string {
+  return `buzz-sheet:admin-draft:${guideId}:${section}`;
+}
+
+export function serializeLocalDraft<Draft>(draft: Draft, serverVersion: number): string {
+  return JSON.stringify({
+    schemaVersion: LOCAL_DRAFT_SCHEMA_VERSION,
+    serverVersion,
+    updatedAt: new Date().toISOString(),
+    draft,
+  } satisfies LocalDraftEnvelope<Draft>);
+}
+
+export function parseLocalDraft<Draft>(serialized: string, parseDraft: (value: unknown) => Draft | null): LocalDraftEnvelope<Draft> | null {
+  try {
+    const value: unknown = JSON.parse(serialized);
+    if (!value || typeof value !== "object") return null;
+    const envelope = value as Record<string, unknown>;
+    if (envelope.schemaVersion !== LOCAL_DRAFT_SCHEMA_VERSION || typeof envelope.serverVersion !== "number" || typeof envelope.updatedAt !== "string") return null;
+    const draft = parseDraft(envelope.draft);
+    return draft === null ? null : {
+      schemaVersion: LOCAL_DRAFT_SCHEMA_VERSION,
+      serverVersion: envelope.serverVersion,
+      updatedAt: envelope.updatedAt,
+      draft,
+    };
+  } catch {
+    return null;
+  }
+}