ci: improve build step

[EdamAme-x]

I have isolated the steps to build.
Because I do not believe that the code for validation of exports should be included in build.ts.

prebuild is executed automatically before the build.

(Also, merging post.ts into build.ts would be a good option)

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.68%. Comparing base (61bee9f) to head (d034266).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3654   +/-   ##
=======================================
  Coverage   91.68%   91.68%           
=======================================
  Files         159      159           
  Lines       10135    10135           
  Branches     2850     2882   +32     
=======================================
  Hits         9292     9292           
  Misses        841      841           
  Partials        2        2           

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