Function appendEntryToFile

src/utils/sessionStorage.ts:2734–2764

(
  fullPath: string,
  entry: Record<string, unknown>,
)

 */
/* eslint-disable custom-rules/no-sync-fs -- sync callers (exit cleanup, materialize) */
function appendEntryToFile(
  fullPath: string,
  entry: Record<string, unknown>,
): void {
  const fs = getFsImplementation()
  const line = jsonStringify(entry) + '\n'
  try {
    fs.appendFileSync(fullPath, line, { mode: 0o600 })
  } catch (error) {
    if (isFsInaccessible(error)) {
      logForDebugging(
        `Skipping sync transcript metadata write for ${fullPath}: ${errorMessage(error)}`,
        { level: 'warn' },
      )
      return
    }
    try {
      fs.mkdirSync(dirname(fullPath), { mode: 0o700 })
      fs.appendFileSync(fullPath, line, { mode: 0o600 })
    } catch (retryError) {
      if (isFsInaccessible(retryError)) {
        logForDebugging(
          `Skipping sync transcript metadata write for ${fullPath}: ${errorMessage(retryError)}`,
          { level: 'warn' },
        )
        return
      }
      throw retryError
    }
  }
}

/**
 * Sync tail read for reAppendSessionMetadata's external-writer check.