feat: Add paced mutations with timing strategies

.changeset/paced-mutations.md

@@ -0,0 +1,49 @@
+---
+"@tanstack/db": patch
+"@tanstack/react-db": patch
+---
+
+Add paced mutations with pluggable timing strategies
+
+Introduces a new paced mutations system that enables optimistic mutations with pluggable timing strategies. This provides fine-grained control over when and how mutations are persisted to the backend. Powered by [TanStack Pacer](https://github.com/TanStack/pacer).
+
+**Key Design:**
+
+- **Debounce/Throttle**: Only one pending transaction (collecting mutations) and one persisting transaction (writing to backend) at a time. Multiple rapid mutations automatically merge together.
+- **Queue**: Each mutation creates a separate transaction, guaranteed to run in the order they're made (FIFO by default, configurable to LIFO).
+
+**Core Features:**
+
+- **Pluggable Strategy System**: Choose from debounce, queue, or throttle strategies to control mutation timing
+- **Auto-merging Mutations**: Multiple rapid mutations on the same item automatically merge for efficiency (debounce/throttle only)
+- **Transaction Management**: Full transaction lifecycle tracking (pending → persisting → completed/failed)
+- **React Hook**: `usePacedMutations` for easy integration in React applications
+
+**Available Strategies:**
+
+- `debounceStrategy`: Wait for inactivity before persisting. Only final state is saved. (ideal for auto-save, search-as-you-type)
+- `queueStrategy`: Each mutation becomes a separate transaction, processed sequentially in order (defaults to FIFO, configurable to LIFO). All mutations are guaranteed to persist. (ideal for sequential workflows, rate-limited APIs)
+- `throttleStrategy`: Ensure minimum spacing between executions. Mutations between executions are merged. (ideal for analytics, progress updates)
+
+**Example Usage:**
+
+```ts
+import { usePacedMutations, debounceStrategy } from "@tanstack/react-db"
+
+const mutate = usePacedMutations({
+  mutationFn: async ({ transaction }) => {
+    await api.save(transaction.mutations)
+  },
+  strategy: debounceStrategy({ wait: 500 }),
+})
+
+// Trigger a mutation
+const tx = mutate(() => {
+  collection.update(id, (draft) => {
+    draft.value = newValue
+  })
+})
+
+// Optionally await persistence
+await tx.isPersisted.promise
+```