chore(vendor): import pi 0.85.1

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: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/coding-agent/test/experimental.test.ts

@@ -0,0 +1,44 @@
+import { afterEach, describe, expect, it } from "vitest";
+import { areExperimentalFeaturesEnabled } from "../src/core/experimental.ts";
+
+describe("areExperimentalFeaturesEnabled", () => {
+	const originalPiExperimental = process.env.PI_EXPERIMENTAL;
+
+	afterEach(() => {
+		if (originalPiExperimental === undefined) {
+			delete process.env.PI_EXPERIMENTAL;
+		} else {
+			process.env.PI_EXPERIMENTAL = originalPiExperimental;
+		}
+	});
+
+	it("returns false when PI_EXPERIMENTAL is unset", () => {
+		delete process.env.PI_EXPERIMENTAL;
+
+		expect(areExperimentalFeaturesEnabled()).toBe(false);
+	});
+
+	it("returns false when PI_EXPERIMENTAL is empty", () => {
+		process.env.PI_EXPERIMENTAL = "";
+
+		expect(areExperimentalFeaturesEnabled()).toBe(false);
+	});
+
+	it("returns true when PI_EXPERIMENTAL is set to 1", () => {
+		process.env.PI_EXPERIMENTAL = "1";
+
+		expect(areExperimentalFeaturesEnabled()).toBe(true);
+	});
+
+	it("returns false when PI_EXPERIMENTAL is set to 0", () => {
+		process.env.PI_EXPERIMENTAL = "0";
+
+		expect(areExperimentalFeaturesEnabled()).toBe(false);
+	});
+
+	it("returns false when PI_EXPERIMENTAL is set to a non-1 value", () => {
+		process.env.PI_EXPERIMENTAL = "true";
+
+		expect(areExperimentalFeaturesEnabled()).toBe(false);
+	});
+});