Revert "fix: Properly configure SDK to be distributed as ESM"

[frederikprijck]

Opening a PR to revert the ESM changes, as there seem to be issues with using the getSession in tools for Gen AI.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 79.68%. Comparing base (c6947e2) to head (cf766f9).

Files with missing lines	Patch %	Lines
src/client/helpers/get-access-token.ts	0.00%	0 Missing and 1 partial ⚠️
src/client/index.ts	0.00%	0 Missing and 1 partial ⚠️
src/server/index.ts	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2046   +/-   ##
=======================================
  Coverage   79.68%   79.68%           
=======================================
  Files          21       21           
  Lines        1925     1925           
  Branches      316      316           
=======================================
  Hits         1534     1534           
  Misses        385      385           
  Partials        6        6           

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