Device: iPad Pro M4, iOS 26.2
Paid developer account
I cloned the repo, ran downloadFrameworks.sh (which completed without error), opened Code.xcodeproj, switched the development team to my team, changed the bundle identifier of Code App and extension to match my organization, set an appropriate App Group and built without issue.
When installed on my iPad, I created "empty" source files containing only the hello world for C, C++, JavaScript and Java.
For C and C++ there is an error message in the Terminal Tab, complaining that "wasm" can't be found, for JavaScript "node" is reported missing, as is "java" and "javac" for Java.
I've attached a dump of what's inside my Resources folder at build time to this issue. Let me know if you need anything else.
Resources.txt
The other languages seem to work, although python executes the script but then crashes with a bus error if the last line is empty.