… for better PATH management, and improve README instructions for setup. The install scripts now auto-configure the user's PATH and provide clearer next steps after installation.

* Fix remaining critical CLI audit items

- Object/array schema params now register as --flag <json> with a
  JSON-parsing argParser; invalid JSON is a usage error
- Derive binary PNG output context from the built body so generated
  commands (universal --headless png) write a PNG, not base64 text
- Map syscall-coded network failures (ENOTFOUND, ECONNREFUSED, ...) in
  the cause chain to exit 7 and render the cause
- setup now rejects as a usage error on EOF/closed stdin instead of
  exiting 0 having saved nothing; handle TTY EOF and Ctrl+D
- Add offline README docs regression test validating documented
  commands and flags against the command tree built from BundledSchema

* Skip parse/markdown defaults for headless png screenshots

Manual end-to-end testing surfaced that generated commands routed PNG
output correctly but applyRequestDefaults still injected markdown:true,
so the API returned markdown instead of a screenshot and PNG extraction
failed. Skip the defaults when headless is png so universal --headless
png writes a real PNG, matching the curated screenshot command.

* Refactor CLI error handling by introducing CliUsageError class

- Moved CliUsageError definition to a new file for better organization.
- Updated imports across multiple files to reference the new location of CliUsageError.
- Added tests for CliUsageError to ensure proper functionality and error message handling.