/**
 * Tiny `{token}` substitution helper for translated strings.
 *
 * Why this exists
 * ---------------
 * Two ad-hoc substitution mechanisms had grown in the SDK:
 *  - per-key country splicing inside `getLocale` (hard-coded, not reusable);
 *  - inline `.replace('{value}', …)` at call sites (curing).
 * Neither escaped values. Since several translated strings are concatenated
 * into HTML and then HTML-parsed by `JsxFromString`, unescaped user input
 * would be an XSS vector. This helper unifies substitution and makes
 * "values may be user-entered" safe by default.
 *
 * Contract
 * --------
 * - The **template** is author-controlled. It may legitimately contain HTML
 *   (`<strong>`, `<ul>`, …) — `JsxFromString` will parse it.
 * - The **values** are escaped. A user value like `<img onerror=…>` renders
 *   inert even when the surrounding template is HTML-parsed.
 * - Tokens are `{name}` (regex `\{(\w+)\}`); repeated and multiple tokens are
 *   both supported (uses a global `replace`).
 * - Unknown tokens are left verbatim so a missing-arg bug is visible in the
 *   UI rather than silently swallowed.
 *
 * Caveats
 * -------
 * Escaped output only renders correctly when the surrounding string is
 * HTML-parsed (i.e. displayed via `JsxFromString`), which decodes the
 * entities back. In a *plain* React text node, `&`, `<`, `>`, `"`, `'` in a
 * substituted value would display as entity references (`&amp;` etc.) — and
 * these are NOT rare: names ("O'Brien"), org names ("Smith & Co"), and
 * country labels ("Antigua & Barbuda") all contain them. So the rule is:
 * anything that shows an interpolated value must render through
 * `JsxFromString`. `StatusMessage`'s callers already do; if you add a new
 * place that interpolates, route it through `JsxFromString` too rather than
 * a bare `{value}` text node.
 */
/**
 * Substitute `{token}`s in `template` with HTML-escaped values from `vars`.
 * Returns `template` verbatim when `vars` is undefined (no allocation).
 */
export declare const interpolate: (template: string, vars: Record<string, string | number> | undefined) => string;