feat(FN-3891): document memory backup settings in settings reference

Documents the memory backup feature in the settings reference and adds a changeset to prepare for publishing.

Fusion-Task-Id: FN-3891

packages/core/src/settings-schema.ts

@@ -240,6 +240,11 @@ export const DEFAULT_PROJECT_SETTINGS = {
   autoBackupSchedule: "0 2 * * *",
   autoBackupRetention: 7,
   autoBackupDir: ".fusion/backups",
+  memoryBackupEnabled: false,
+  memoryBackupSchedule: "0 3 * * *",
+  memoryBackupRetention: 14,
+  memoryBackupDir: ".fusion/backups/memory",
+  memoryBackupScope: "all" as const,
   autoSummarizeTitles: false,
   useAiMergeCommitSummary: true,
   titleSummarizerProvider: undefined,