Add coloured JSON output with --pretty and Ctrl+T

[WietseWind]

Large JSON replies are hard to read on one line. Add optional indentation and colours.

Changes

• Add --pretty to start with indented, coloured JSON output. Without this
  flag, formatting starts off.
• Press Ctrl+T to turn formatting off or on for new messages. Show the current
  state. Keep the draft and cursor intact.
• Use --no-color for indentation only. Do not write colour reset codes when
  colours are disabled.
• Support connect and listen mode. Keep sent messages, non-JSON messages,
  binary messages, and piped output unchanged.

Demo

Full demo: 13 seconds, 1 MB GIF.

Security overview

• No npm packages added, removed, or updated. Existing commander, ws,
  https-proxy-agent, and read remain in use.
• Reuse Node's readline, tty, and event handling. Add the built-in stream
  module for Ctrl+T input handling. Tests also use built-in util.
  These modules ship with Node.js; no extra package downloads or install scripts.
• Use JSON.parse to validate messages, then format the original tokens with
  string operations and ANSI colours. Do not execute message text.
  Keep large numbers, duplicate keys, and string escapes intact.
  Formatting adds no file writes or network requests.

Validation

• All 20 tests pass on Node.js 18.20.8 and 24.11.1.
• Test the standalone packed package in a macOS terminal: startup flag,
  Ctrl+T, exact numbers, cursor position, and ordinary arrow recall.
• Tests are excluded from the npm package.