omp's canonical getPackageDir() returns undefined inside a bun --compile
binary (import.meta.dir is /$bunfs/root, no owning package.json — issue
#1423). Re-exporting it directly broke pi's string-valued contract:
legacy extensions doing path.join(getPackageDir(), ...) crashed at
runtime in the shipped binary, the primary distribution.
Wrap the canonical helper so the shim always returns a string, falling
back to the executable's directory in compiled mode (where the binary is
the install root). PI_PACKAGE_DIR and dev/source/npm-dist walk-up still
win. Test covers the compiled-mode fallback via isCompiledBinary spy.
Fixes#5968
roboomp
5082763d49