test: add StackForge CLI UX smoke coverage

[rogerchappel]

Summary

• Add a dedicated CLI UX smoke script under tests/.
• Cover JSON output parsing for templates, dry-run init, write init, overwrite refusal, and force overwrite.
• Cover invalid template and invalid --var exit behavior without writing target directories.

Verification

• Tests or checks run:
  • pnpm check
  • pnpm build
  • pnpm check:templates
  • pnpm smoke:init
  • bash tests/cli-ux-smoke.sh
• Manual review completed:
  • Reviewed the staged test-only diff and kept changes scoped to tests/**.

Risk Level

• Low
• Medium
• High

Notes:

Test-only coverage addition. No CLI implementation, templates, production, auth, billing, or secret paths changed.

Rollback Plan

• Revert test: add StackForge CLI UX smoke coverage.

Human Decision Needed

• None
• Maintainer review
• Product/design decision
• Security/privacy review
• Other: