Is there a scripting SDK that I can use to write scripts for Photoshop CC?

You don't "need" special software, it just helps. JavaScript does not need to be "compiled".

ExtendScript/JavaScript can be written in a plain text editor and saved with a .jsx extension rather than .txt – however, some editors are more capable than others when it comes to various scripting languages. For example, there are packages for Atom that can make the job easier.

There is even a webpage app to help write these scripts:

https://ovid-editor.web.app/PHXS

https://ovid-editor.web.app/

The Adobe ExtendScript Toolkit is depreciated software that should be available via your Creative Cloud installer app.

Otherwise, have you tried a web search?

Adobe have moved on from ESTK and now provide a debugger extension for MS Visual Studio Code program:

https://code.visualstudio.com/download

https://marketplace.visualstudio.com/items?itemName=Adobe.extendscript-debug

https://medium.com/adobetech/extendscript-debugger-1-1-0-released-5f2e1a068e89

https://medium.com/adobetech/extendscript-debugger-for-visual-studio-code-public-release-a2ff6161fa01

There are a few things that I miss from the old ESTK app, most notably the Object Model Viewer (I now just use the PDF or an online DOM reference) – however, I have now stopped using the ESTK as I find that I am generally more productive in a modern editor.