`#jni_call(void)(target, "name", "sig")` (3 args before the first
string literal) should work inside an enclosing `#jni_env(env) { ... }`
scope, picking up the env from the block's value directly. Today's
lowering expects 4+ args and errors with "#jni_call requires env,
target, method name, and signature".
The make-green follow-up adds a lowering-side env stack maintained
across the `#jni_env` body walk, and a disambiguation in
`lowerJniCall` that detects "env omitted" via the position of the
first string-literal arg (method name at index 1 → omitted; at index
2 → explicit env).
e463385404