feat(userspace): shell runs programs (ls, cat) via spawn w/ terminal+storage+args page; ext4 holes read as zeros; storage re-attach same buffer

Makefile

@@ -55,7 +55,7 @@ build:
 		-p init -p echo -p snake \
 		-p display-qemu -p input-qemu -p storage-qemu \
 		-p log-server -p permission-manager -p session-server -p smptest -p spawntest -p hello \
-		-p terminal-server -p shell
+		-p terminal-server -p shell -p cat -p ls
 	cargo build --target $(RISCV_TARGET) --release -p adapter-riscv
 
 image: build