/**
 * Frontmatter version upsert.
 *
 * After `vskill skill publish` succeeds, the registry returns the new
 * version (which may have been auto-bumped server-side). To prevent the
 * "phantom update available immediately after install" trap recorded in
 * project_skill_version_publish_desync.md, the CLI writes the registry
 * version back to the source SKILL.md frontmatter so that the next
 * `vskill outdated` poll sees identical local + remote versions.
 *
 * Increment 0794 — US-002b / T-004.
 */
/**
 * Insert or replace the top-level `version:` field in YAML frontmatter.
 *
 * Behaviour:
 *   - If `version:` exists at column 1: replace its value (preserves
 *     surrounding lines and quoting style of the source whenever possible).
 *   - Else if `description:` exists at column 1: insert immediately after
 *     the description block (skipping indented continuation lines).
 *   - Else: append the version line at the end of the frontmatter.
 *   - If the file has no frontmatter block at all: synthesise a minimal one.
 *   - Indented `metadata.version` is never touched.
 *
 * Returns the full file content with the change applied. Pure function.
 */
export declare function upsertFrontmatterVersion(content: string, newVersion: string): string;
/**
 * Lightweight validation: round-trip the result through the frontmatter regex
 * and ensure we still have a valid `---\n...\n---` block. Used by submit.ts
 * as a defensive guard before writing back to disk (AC-US2b-04).
 */
export declare function validatesAsYamlFrontmatter(content: string): boolean;
