CliError used to live in cli.ts and was imported by configFile.ts purely
to grab a one-line class — the dependency arrow said 'config-file loader
depends on the CLI parser' when really it just needed a shared error
type.
Moving CliError to its own errors.ts module flattens the graph:
errors.ts (no internal deps)
|
+-- cli.ts
+-- configFile.ts
+-- config.ts (will use it in the next commit)
cli.ts re-exports CliError for any consumer that prefers to keep
importing it from there; the canonical home is now errors.ts.
