Use the 09:18 judge diagnostics to correct the test-image layout assumption. The EXT4 root directory contains lost+found, glibc, and musl rather than basic_testcode.sh directly.

Change directory lookup helpers to return the matched EXT4 inode number. Add generic inode loading across block groups, enter the glibc and musl directory inodes, and search each directory independently for basic_testcode.sh.

Run the selected basic compatibility group once for the glibc path and once for the musl path, matching the two independent basic-glibc and basic-musl result columns. Keep bounded directory-entry diagnostics for both libc directories so the next run exposes any deeper layout.

Update README.md and DESIGN.md with the observed root layout and the corrected traversal strategy. Verification: git diff --check passed with only Windows CRLF warnings. Full cross-build remains unavailable in this Windows Codex environment.