CVE-2026-71871: Orval: Import-time RCE via header-parameter default -> zod module-level template literal

Orval’s zod schema generation emits the header-parameter default value as a module-level template literal (export const Default = ;) without escaping ${ or the backtick. A default of the form v${<code>}w injects a live JavaScript expression evaluated when the generated zod schema module is imported, executing attacker-controlled code at import — no request or function call needed. Verified on Orval 8.19.0; survives default OpenAPI validation.