Infra: Fix typespec generation on Windows

[yeikel]

What changes did you make? (Give an overview)

Improve the generation of the typespec so that it is portable and works on Windows as well

Is there anything you'd like reviewers to focus on?

Running the build in Windows fails because the format of the command is not correct

Task :contract-typespec:generateOpenApi_api FAILED
'\tsp' is not recognized as an internal or external command,
operable program or batch file.

[Incubating] Problems report is available at: file:///D:/dev/kafka-ui/build/reports/problems/problems-report.html

FAILURE: Build failed with an exception.

• What went wrong:
  Execution failed for task ':contract-typespec:generateOpenApi_api'.

Process 'command 'D:\dev\kafka-ui\contract-typespec.gradle\nodejs\node-v22.12.0-win-x64\npm.cmd'' finished with non-zero exit value 1

How Has This Been Tested? (put an "x" (case-sensitive!) next to an item)

• Manually (please, describe, if necessary)

gradlew.bat clean build works now on Windows

• Unit checks
• Integration checks
• Covered by existing automation

Checklist (put an "x" (case-sensitive!) next to all the items, otherwise the build will fail)

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• My changes generate no new warnings (e.g. Sonar is happy)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

A picture of a cute animal (not mandatory but encouraged)

[yeikel]

@Haarolean Could you please review this?

I contribute from a Windows machine and this would help me :)

[Haarolean]

I contribute from a Windows machine

oof, stay strong