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/15-system-prompt.ts

@@ -0,0 +1,93 @@
+// System prompt sections and per-conversation instructions.
+// Run from packages/durable:
+//   node --conditions=source --experimental-strip-types test/examples/15-system-prompt.ts
+import { BACKGROUND_CONTEXT } from "@earendil-works/chord/context";
+import { createModels } from "@earendil-works/pi-ai/models";
+import { fauxAssistantMessage, fauxProvider } from "@earendil-works/pi-ai/providers/faux";
+import { NodeExecutionEnv } from "../../src/env/node.ts";
+import {
+	type Conversation,
+	createRegistry,
+	defineExtension,
+	Harness,
+	MemoryStorage,
+	SystemEntry,
+	section,
+	wrapSection,
+} from "../../src/index.ts";
+
+const context = BACKGROUND_CONTEXT;
+const faux = fauxProvider();
+const models = createModels();
+models.setProvider(faux.provider);
+faux.setResponses([fauxAssistantMessage("Done."), fauxAssistantMessage("Done."), fauxAssistantMessage("Done.")]);
+
+// Pico stores no prompt state. Before each model request, the sections of the
+// conversation's selected extensions render the desired prompt, and only the
+// difference to what the model already saw is appended to the transcript as a
+// `pi.system` entry.
+const Coding = defineExtension({
+	name: "coding",
+	sections: [
+		// `tag: false` sends the text as is; by default it is wrapped in <key>...</key>.
+		section("preamble", () => "You are a coding agent.", { tag: false }),
+		// Sections see the environment built for this request, here its working directory.
+		section("cwd", (input) => input.env?.cwd),
+	],
+});
+const AgentsMd = defineExtension({
+	name: "agents-md",
+	sections: [section("agents_md", () => "Run npm run check after changes.")],
+});
+// Another extension decorates a section by key without replacing it.
+const Terse = defineExtension({
+	name: "terse",
+	wraps: [
+		wrapSection("preamble", (preamble) => ({
+			...preamble,
+			render: async (input, renderContext) => `${await preamble.render(input, renderContext)} Be terse.`,
+		})),
+	],
+});
+
+const registry = createRegistry();
+registry.install(Coding);
+registry.install(AgentsMd);
+registry.install(Terse);
+// The environment follows each conversation's agent `cwd`.
+const env = ({ cwd = "/" }: { readonly cwd?: string }) => new NodeExecutionEnv({ cwd });
+const harness = await Harness.open(new MemoryStorage(), { models, registry, env }, context);
+const model = { provider: "faux", modelId: "faux-1" };
+const root = await harness.root(context, { agent: { model, cwd: "/repo" } });
+
+// A subagent deselects AGENTS.md and gets its own instructions, rendered last
+// as the `instructions` section.
+const subagent = await harness.createConversation(
+	{
+		ownership: { kind: "ownerless" },
+		agent: {
+			model,
+			cwd: "/repo",
+			extensions: { remove: [AgentsMd] },
+			instructions: "Only read; never edit files.",
+		},
+	},
+	context,
+);
+
+async function systemEntries(conversation: Conversation) {
+	const page = await conversation.entries({}, 20, undefined, context);
+	return [...page.items].reverse().flatMap((entry) => (SystemEntry.is(entry) ? (entry.model ?? []) : []));
+}
+
+await (await root.submit({ type: "input", content: "Fix the build." }, context)).wait(context);
+await (await subagent.submit({ type: "input", content: "Read the logs." }, context)).wait(context);
+console.log("root system prompt:", await systemEntries(root));
+console.log("subagent system prompt:", await systemEntries(subagent));
+
+// When a section's output changes, the next request appends only the change.
+await root.configure({ cwd: "/repo/packages" }, context);
+await (await root.submit({ type: "input", content: "Now the package." }, context)).wait(context);
+console.log("root system entries after cwd change:", await systemEntries(root));
+
+await harness.close(context);