Polish CLI snapshot experience

[a-github-name]

Summary

• remove the public mere tui surface in favor of mere onboard --interactive
• group app manifest commands by nested surface for easier command discovery
• make mere ops workspace-snapshot human-friendly by default with stderr progress and a compact stdout summary while keeping --json clean
• bump package and fallback CLI version to 0.2.2

Verification

• pnpm check
• pnpm lint
• pnpm test
• pnpm smoke
• git diff --check

Note: local Node reports v26.0.0, so pnpm prints the existing engine warning for >=24 <26, but all commands pass.