feat: enforce review preflight coverage and budgets

[EmersonBraun]

Summary

Closes #45.

• Adds provider-free --plan / --dry-run output, including JSON.
• Refuses file, byte, snapshot, and provider-call overages before the first model call, with reductions.
• Enforces bounded maxCalls (absolute ceiling 1000), CLI concurrency default 1, and one retry only for invalid structured output.
• Marks required-lens failures and unreviewed coverage as INCOMPLETE with exit code 2; --no-fail remains findings-only.
• Adds config, CLI smoke, retry, and preflight coverage tests plus docs/changelog updates.

Verification

• npm run check
• npm pack --dry-run
• git diff --check
• 50 tests passing locally.