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/tui/test/tui-shrink.test.ts

@@ -0,0 +1,45 @@
+import assert from "node:assert";
+import { describe, it } from "node:test";
+import type { Component, TUI } from "../src/tui.ts";
+import { TuiMainScreen } from "../src/tui-main-screen.ts";
+import { VirtualTerminal } from "./virtual-terminal.ts";
+
+class Lines implements Component {
+	private lines: string[];
+
+	constructor(lines: string[]) {
+		this.lines = lines;
+	}
+
+	render(): string[] {
+		return this.lines;
+	}
+
+	invalidate(): void {}
+}
+
+describe("TUI shrinking content", () => {
+	it("clears all rendered lines when content shrinks to zero", async () => {
+		const terminal = new VirtualTerminal(40, 10);
+		const tui: TUI = new TuiMainScreen(terminal);
+		const content = new Lines(["first", "second", "third"]);
+		tui.addChild(content);
+		tui.start();
+		await terminal.waitForRender();
+
+		assert.ok(terminal.getViewport().some((line) => line.includes("first")));
+		assert.ok(terminal.getViewport().some((line) => line.includes("second")));
+		assert.ok(terminal.getViewport().some((line) => line.includes("third")));
+
+		tui.clear();
+		tui.requestRender();
+		await terminal.waitForRender();
+
+		const viewport = terminal.getViewport();
+		assert.ok(!viewport.some((line) => line.includes("first")), "first line should be cleared");
+		assert.ok(!viewport.some((line) => line.includes("second")), "second line should be cleared");
+		assert.ok(!viewport.some((line) => line.includes("third")), "third line should be cleared");
+
+		tui.stop();
+	});
+});