feat(cli): add clearance real-smoke prep gate

[ChechiDev]

Closes #147

Summary

• Adds CP1.6h clearance real-smoke preparation gate behavior.
• Keeps execution gated to preparation only; no real smoke execution is included in this PR.

Changes

File	Change
cli/main.py	Adds the CLI prep gate behavior for clearance real-smoke readiness.
tests/unit/cli/test_smoke_clearance_real_prep_gate.py	Adds unit coverage for gate contracts and option handling.

Size exception

• Size exception: PASS from preflight; PR exceeds the normal review-size target because the gate contract coverage is intentionally bundled with the CLI change.

Test plan

• Not run per CP1.6h-PUSH-PR-001 instruction: no tests.
• Real smoke not run per instruction: no real smoke.

Contributor checklist

• Linked an approved issue: feat(cp1): add CP1.6h real-smoke preparation gate #147 has status:approved.
• Added exactly one type:* label: type:feature.
• No documentation files changed.
• No real-smoke execution performed.
• Conventional commit format verified.
• No Co-Authored-By trailers added.