Require Node.js 22+ and remove picocolors

[ho991217]

Context

The package currently has no engines.node requirement and uses picocolors for terminal styling. Setting Node.js 22 as the minimum supported version allows us to use the built-in util.styleText API and remove this dependency.

Proposed work

• Set engines.node to >=22 in package.json.
• ㅓReplace picocolors usage with styleText from node:util.
• Remove picocolors from dependencies and update the lockfile.

Acceptance criteria

• CLI output retains its existing colors and emphasis.
• Color output remains appropriate for interactive terminals and redirected output.
• The CLI works on Node.js 22 and newer supported versions.