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/src/components/alt-screen-flash.ts

@@ -0,0 +1,51 @@
+import type { Component } from "../tui.ts";
+import { truncateToWidth } from "../utils.ts";
+
+const DEFAULT_DURATION_MS = 1000;
+
+interface FlashEntry {
+	id: number;
+	message: string;
+	timer: NodeJS.Timeout;
+}
+
+/** Transient messages composited by the alternate-screen renderer. */
+export class AltScreenFlashContainer implements Component {
+	private readonly entries: FlashEntry[] = [];
+	private nextId = 0;
+	private readonly requestRender: () => void;
+
+	constructor(requestRender: () => void) {
+		this.requestRender = requestRender;
+	}
+
+	flash(message: string, durationMs = DEFAULT_DURATION_MS): void {
+		const id = this.nextId++;
+		const timer = setTimeout(
+			() => {
+				const index = this.entries.findIndex((entry) => entry.id === id);
+				if (index === -1) return;
+				this.entries.splice(index, 1);
+				this.requestRender();
+			},
+			Math.max(0, durationMs),
+		);
+		timer.unref();
+		this.entries.push({ id, message, timer });
+		this.requestRender();
+	}
+
+	dispose(): void {
+		for (const entry of this.entries) clearTimeout(entry.timer);
+		this.entries.length = 0;
+	}
+
+	invalidate(): void {}
+
+	render(width: number): string[] {
+		return this.entries.map((entry) => {
+			const message = truncateToWidth(` ${entry.message} `, width, "");
+			return `\x1b[7m${message}\x1b[27m`;
+		});
+	}
+}