Add export method dialog, extract shared Dialog primitive

Add export dialog with download/clipboard options and optional
undo/redo history inclusion (default off). Extract shared Dialog
component to ui/dialog.tsx, consolidating open/close lifecycle,
backdrop click, and escape key handling from all 6 dialog components.
Update spec to reflect export method dialog and optional history.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/components/import-confirm-prompt.tsx

@@ -1,5 +1,5 @@
-import { useEffect, useRef } from "react";
 import { Button } from "./ui/button.js";
+import { Dialog } from "./ui/dialog.js";
 
 interface ImportConfirmDialogProps {
 	open: boolean;
@@ -12,38 +12,8 @@ export function ImportConfirmDialog({
 	onConfirm,
 	onCancel,
 }: Readonly<ImportConfirmDialogProps>) {
-	const dialogRef = useRef<HTMLDialogElement>(null);
-
-	useEffect(() => {
-		const dialog = dialogRef.current;
-		if (!dialog) return;
-		if (open && !dialog.open) dialog.showModal();
-		else if (!open && dialog.open) dialog.close();
-	}, [open]);
-
-	useEffect(() => {
-		const dialog = dialogRef.current;
-		if (!dialog) return;
-		function handleCancel(e: Event) {
-			e.preventDefault();
-			onCancel();
-		}
-		function handleBackdropClick(e: MouseEvent) {
-			if (e.target === dialog) onCancel();
-		}
-		dialog.addEventListener("cancel", handleCancel);
-		dialog.addEventListener("mousedown", handleBackdropClick);
-		return () => {
-			dialog.removeEventListener("cancel", handleCancel);
-			dialog.removeEventListener("mousedown", handleBackdropClick);
-		};
-	}, [onCancel]);
-
 	return (
-		<dialog
-			ref={dialogRef}
-			className="m-auto rounded-lg border border-border bg-card p-6 text-foreground shadow-xl backdrop:bg-black/50"
-		>
+		<Dialog open={open} onClose={onCancel}>
 			<h2 className="mb-2 font-semibold text-lg">Replace current encounter?</h2>
 			<p className="mb-4 text-muted-foreground text-sm">
 				Importing will replace your current encounter, undo/redo history, and
@@ -57,6 +27,6 @@ export function ImportConfirmDialog({
 					Import
 				</Button>
 			</div>
-		</dialog>
+		</Dialog>
 	);
 }