fs rewrite stage 3: nested directories, paths, cwd (cd/mkdir/ls)

- directories generalized: dir_find/dir_add/dir_remove take any dir inode;
  every dir carries '.'/'..'. Path resolution (resolve / resolve_parent) walks
  absolute or cwd-relative paths; open/mkdir/chdir/remove/opendir take paths.
- per-process cwd: PROC_CWD in the PCB (root by default, inherited on fork);
  sys_chdir sets it, sys_opendir points ls at any directory.
- shell: 'cd' builtin + cwd-aware prompt; 'mkdir'/'ls <dir>' tools; 'exit'/'quit'
  and EOF call poweroff() (clean shutdown via the $ED opcode -> reliable save).
- three HL/buffer-clobber bugs fixed along the way: resolve didn't preserve the
  path cursor across dir_find; cur_cwd clobbered HL; resolve_parent set the final
  name before resolve() overwrote wFsNameBuf (now copied after).
- verified: nested mkdir/cd/save, multi-level paths (cat docs/sub/b), and the
  whole tree persists across a reboot.
- README: document directories + the poweroff opcode.

1 files changed, 1 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 87a7d9d..58a6bd1 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,7 @@ $(BUILD)/%.o: src/%.asm | $(BUILD)
 # C programs: compiled with SDCC into ROM-bank blobs and INCBIN'd by programs.asm
 CBLOBS := c/chello.bin c/echo.bin c/true.bin c/false.bin c/uname.bin \
           c/pid.bin c/cat.bin c/wc.bin c/head.bin c/args.bin \
-          c/ls.bin c/save.bin c/rm.bin c/sh.bin c/ps.bin c/kill.bin c/spin.bin c/blk.bin
+          c/ls.bin c/save.bin c/rm.bin c/sh.bin c/ps.bin c/kill.bin c/spin.bin c/blk.bin c/mkdir.bin
 $(BUILD)/programs.o: $(CBLOBS)
 
 # C programs also depend on the shared libc sources