🐛 Bug: [secret-messages] project-level tsc fails

[JoshuaKGoldberg]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.
• This is the appropriate issue form for the bug I would like to report.

Expected

npm run tsc in secret-messages should pass. check-solutions.sh "tsc" runs it in every project.

Actual

It fails, and has since #82:

02-allowed-imports/index.ts(1,20): error TS7016: Could not find a declaration file for module './answer.js'.
02-allowed-imports/index.ts(2,26): error TS2732: Cannot find module './guesses.json'.
02-allowed-imports/index.ts(8,33): error TS2532: Object is possibly 'undefined'.

It's the only one of the 30 projects that fails. Unnoticed because the all-projects sweep only runs when a PR touches no projects/** files.

Impacted Project

configuration-options/secret-messages

Additional Info

A project-level tsc never reads step TSConfigs, so allowJs and resolveJsonModule are missing, and message.codePointAt(i) is number | undefined under strict. Blocks #337.