Function parseShellFrontmatter

src/utils/frontmatterParser.ts:351–370

(
  value: unknown,
  source: string,
)

 * and other fields degrade.
 */
export function parseShellFrontmatter(
  value: unknown,
  source: string,
): FrontmatterShell | undefined {
  if (value == null) {
    return undefined
  }
  const normalized = String(value).trim().toLowerCase()
  if (normalized === '') {
    return undefined
  }
  if ((FRONTMATTER_SHELLS as readonly string[]).includes(normalized)) {
    return normalized as FrontmatterShell
  }
  logForDebugging(
    `Frontmatter 'shell: ${value}' in ${source} is not recognized. Valid values: ${FRONTMATTER_SHELLS.join(', ')}. Falling back to bash.`,
    { level: 'warn' },
  )
  return undefined
}