fix(analyze): require flush before assertions

[lntutor]

Summary

• add the first-stage askr/testing-contract check for stale post-dispatch assertions
• require an awaited flush() before the next expect/assert in the same block
• scope detection to canonical imports from @askrjs/askr/testing, including aliases

Closes #50.

Test plan

• npm test -- tests/analyze.rules.test.ts
• npm run check

[lntutor]

Superseded by #58, which landed the testing-contract flush rule and coverage on main. Closing this duplicate to keep the review queue clean.