NO_COLOR and TTY detection

When mytool list > out.txt writes \x1b[32mOK\x1b[0m into the file, the user opens out.txt and sees escape-code garbage. When CI logs capture ANSI codes as ^[[32m, grep patterns break. When a blind user's screen reader hits color codes, output becomes unintelligible. The NO_COLOR convention (no-color.org) and TTY detection exist for exactly this reason — ignoring them corrupts piped output, log files, and accessibility tooling.

Check process.env.NO_COLOR and process.stdout.isTTY before emitting ANSI codes, or use a library like picocolors that does this automatically. Wire the check once in src/cli/lib/color.ts:

import pc from 'picocolors'
// picocolors honors NO_COLOR and isTTY automatically
console.error(pc.green('Success'))

Test with NO_COLOR=1 mytool list and mytool list | cat.