feat(storage): ext4-only disk via mkfs.ext4 -d; drop FAT16; feature-gated mount (ro on unknown ro_compat); ext4 read spans blocks, delete clears inode, mkdir counts dir; virtio-blk writes; test-qemu e2fsck gate

crates/init/src/manifest.rs

@@ -70,6 +70,7 @@ pub const SERVERS: &[Program] = &[
 /// spawns through init, then reports and halts.
 pub const TESTS: &[Program] = &[Program {
     serves: false,
+    uses: &["storage"],
     spawns: Some(Limits { pages: 128, endpoints: 2, notifications: 2, regions: 2 }),
     system_control: true,
     ..server("spawntest", b"spawntst.elf", SMALL)