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/chord/test/delta-clone.test.ts

@@ -0,0 +1,53 @@
+import { describe, expect, it } from "vitest";
+import { apply, track } from "../src/delta/index.ts";
+
+describe("tracker ownership", () => {
+	it("takes immutable ownership of the imported revision in O(1)", () => {
+		const input = {
+			point: { x: 3, y: 7, pressure: 0.1 },
+			rows: [{ values: [0, false, null, "text", { n: 1 }] }],
+		};
+		const tracker = track(input);
+		expect(tracker.value).toBe(input);
+		expect(tracker.value.point).toBe(input.point);
+		expect(tracker.value.rows[0]!.values[4]).toBe(input.rows[0]!.values[4]);
+		expect(Object.isFrozen(tracker.value.rows[0]!.values)).toBe(false);
+	});
+
+	it("preserves null prototypes in an alias-free owned root", () => {
+		type Dictionary = { enabled: boolean; child: { n: number } };
+		const dictionary = Object.assign(Object.create(null) as Dictionary, { enabled: true, child: { n: 1 } });
+		const tracker = track({ dictionary, left: { nested: [{ n: 1 }] }, right: { nested: [{ n: 1 }] } });
+		expect(Object.getPrototypeOf(tracker.value.dictionary)).toBeNull();
+		expect(tracker.value.dictionary).toBe(dictionary);
+		expect(tracker.value.left).not.toBe(tracker.value.right);
+		expect(tracker.value.left.nested[0]).not.toBe(tracker.value.right.nested[0]);
+	});
+
+	it("does not traverse a trusted root while taking ownership", () => {
+		let reads = 0;
+		const input = Object.defineProperty({}, "untrustedAccessor", {
+			enumerable: true,
+			get() {
+				reads += 1;
+				throw new Error("root was traversed");
+			},
+		});
+		const tracker = track(input);
+		expect(tracker.value).toBe(input);
+		expect(reads).toBe(0);
+	});
+
+	it("copies assigned and inserted values immediately", () => {
+		const tracker = track({ rows: [] as { nested: { value: number } }[] });
+		const assigned = { nested: { value: 1 } };
+		const change = tracker.beginChange();
+		change.state.rows.push(assigned);
+		assigned.nested.value = 9;
+		expect(change.state.rows[0]!.nested.value).toBe(1);
+		const prepared = change.prepare();
+		expect(prepared.value.rows[0]!.nested.value).toBe(1);
+		const replica = apply(structuredClone(prepared.base), prepared.ops);
+		expect(replica).toEqual(prepared.value);
+	});
+});