chore(vendor): import pi 1.3.0

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0

third_party/pi/packages/durable/test/examples/05-watches.ts

@@ -0,0 +1,41 @@
+// Serialize asynchronous document work with a watch.
+// Run from packages/durable:
+//   node --conditions=source --experimental-strip-types test/examples/05-watches.ts
+import { BACKGROUND_CONTEXT } from "@earendil-works/chord/context";
+import { createSession, defineDoc, MemoryStorage } from "../../src/index.ts";
+
+const context = BACKGROUND_CONTEXT;
+const session = createSession(new MemoryStorage());
+
+const Notes = defineDoc<{ text: string }>({
+	kind: "example.notes",
+	version: 1,
+	scope: "conversation",
+	history: "rewindable",
+	fork: "asOf",
+	initial: () => ({ text: "" }),
+});
+const chat = await session.commit(async (tx) => {
+	const conversation = await tx.createConversation({ ownership: { kind: "ownerless" } });
+	(await tx.doc(Notes, conversation.id)).text = "first";
+	return conversation;
+}, context);
+
+// A watch starts from one stable acquisition revision. Slow callbacks never
+// overlap; exact committed frames buffer, with a full-value reset after 100.
+const notesWatch = await session.watchDoc(Notes, chat.id, context);
+if (notesWatch === undefined) throw new Error("notes are absent");
+console.log("watch baseline:", notesWatch.value);
+const delivered = new Promise<void>((resolve) => {
+	notesWatch.start(async (value, _ops, _deliveryContext) => {
+		console.log("watch update:", value);
+		resolve();
+	});
+});
+await session.commit(async (tx) => {
+	(await tx.doc(Notes, chat.id)).text = "observed asynchronously";
+}, context);
+await delivered;
+await notesWatch.stop();
+
+await session.close(context);