style: mute onboarding description text

[0xroylee]

What Changed

• Added a shared renderCliMutedText() helper in packages/cli/src/utils/terminal-format.ts for subdued CLI text rendering.
• Updated onboarding intro output in packages/cli/src/features/onboard/wizard.ts so the descriptive lines render in gray while keeping the heading and next-command box unchanged.
• Added focused onboarding regression coverage in packages/cli/tests/onboard-next-command.test.ts.

Why

• The onboarding description needed a lighter visual weight so the key action items stand out more clearly after successful setup.
• This keeps the onboarding flow readable without changing the existing devos daemon guidance.

How to Test

• Run the CLI onboarding test file and confirm the intro text and next-command behavior still pass.
• Run the full CLI/unit suite and confirm the new muted-text helper and onboarding output remain stable.
• Expected outcome: the onboarding description renders in gray, and the boxed devos daemon next command still appears after the doctor checks.

Additional Notes

• The change is intentionally narrow: it only affects onboarding description styling.
• I preserved the existing next-command guidance and kept the renderer helper reusable for other CLI copy later.