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/11-extension-state.ts

@@ -0,0 +1,86 @@
+// An extension that keeps its own per-conversation document.
+// Run from packages/durable:
+//   node --conditions=source --experimental-strip-types test/examples/11-extension-state.ts
+import { BACKGROUND_CONTEXT } from "@earendil-works/chord/context";
+import { Type } from "@earendil-works/pi-ai";
+import { createModels } from "@earendil-works/pi-ai/models";
+import { fauxAssistantMessage, fauxProvider, fauxToolCall } from "@earendil-works/pi-ai/providers/faux";
+import {
+	createRegistry,
+	defineDoc,
+	defineExtension,
+	defineTool,
+	Harness,
+	MemoryStorage,
+	section,
+} from "../../src/index.ts";
+
+const context = BACKGROUND_CONTEXT;
+
+// A todo list per conversation. Rewindable with `asOf`, so a fork starts with
+// the todos its parent had at the fork entry.
+const Todos = defineDoc<{ items: string[] }>({
+	kind: "example.todos",
+	version: 1,
+	scope: "conversation",
+	history: "rewindable",
+	fork: "asOf",
+	initial: () => ({ items: [] }),
+});
+
+// The tool writes the document; the section shows it to the model before every
+// request. Nothing needs to create it up front: tx.doc() creates it on first
+// write, and the section treats a missing document as an empty list.
+const Todo = defineExtension({
+	name: "todo",
+	tools: [
+		defineTool({
+			name: "todo",
+			description: "Add an item to your todo list",
+			parameters: Type.Object({ item: Type.String() }),
+			execute: async (args, api, callContext) => {
+				await api.commit(async (tx) => {
+					(await tx.doc(Todos, api.conversationId)).items.push(args.item);
+				}, callContext);
+				return { output: [{ type: "text", text: `added ${args.item}` }] };
+			},
+		}),
+	],
+	sections: [
+		section("todos", async (input, renderContext) => {
+			const todos = await input.read.snapshot(Todos, input.conversationId, renderContext);
+			return todos === undefined || todos.items.length === 0 ? undefined : todos.items.join("\n");
+		}),
+	],
+});
+
+const faux = fauxProvider();
+const models = createModels();
+models.setProvider(faux.provider);
+const registry = createRegistry();
+registry.install(Todo);
+const harness = await Harness.open(new MemoryStorage(), { models, registry }, context);
+const root = await harness.root(context, { agent: { model: { provider: "faux", modelId: "faux-1" } } });
+
+faux.setResponses([
+	fauxAssistantMessage(fauxToolCall("todo", { item: "fix the build" }), { stopReason: "toolUse" }),
+	fauxAssistantMessage("Noted."),
+	fauxAssistantMessage("Working on it."),
+]);
+await (await root.submit({ type: "input", content: "Remember to fix the build." }, context)).wait(context);
+console.log("todos:", await harness.snapshot(Todos, root.id, context));
+
+// The next request's system prompt carries the list. The first system message
+// only announced the todo tool; no section had text yet.
+await (await root.submit({ type: "input", content: "What is next?" }, context)).wait(context);
+const { messages } = await root.context(context);
+console.log(
+	"system messages:",
+	messages.flatMap((message) =>
+		message.role === "system"
+			? [{ sections: message.sections, toolsAdded: message.toolsAdded?.map((tool) => tool.name) }]
+			: [],
+	),
+);
+
+await harness.close(context);