fs rewrite stage 1: persistent block device (bounce buffer, cart SRAM)

- blk.asm: read_block/write_block move 256-byte blocks between battery-backed
  cart-RAM banks (8-11, the 'disk') and a WRAM bounce buffer. Banking is hidden
  in those two routines; they inline the 'restore my bank' step so they never
  touch the stack while the disk bank is mapped over the process's $A000 window
  (the stack lives there too -- a call/ret would rug-pull it).
- format-on-first-boot: superblock magic in block 0; otherwise the disk persists.
- cart RAM bumped to 128 KiB (-r 4); process banks 0-7, disk banks 8-11.
- debug tool 'blk fill/peek' + syscalls to validate round-trip and persistence.
- verified: round-trip incl. cross-bank (block 100 -> bank 11); block survives a
  reboot via .sav; magic intact (no reformat on 2nd boot).
- old WRAM 8-slot FS still backs the tools until stages 2-3.

1 files changed, 2 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index a3a4b2b..87a7d9d 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ OBJS     := $(patsubst src/%.asm,$(BUILD)/%.o,$(SRCS))
 
 ASFLAGS  := -I include -Wall
 # MBC5 + RAM + battery; -r 3 = 32 KiB cart RAM (bump for more task banks)
-FIXFLAGS := -v -m MBC5+RAM+BATTERY -r 3 -p 0xFF -t GBOS
+FIXFLAGS := -v -m MBC5+RAM+BATTERY -r 4 -p 0xFF -t GBOS
 
 .PHONY: all clean run
 
@@ -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/ls.bin c/save.bin c/rm.bin c/sh.bin c/ps.bin c/kill.bin c/spin.bin c/blk.bin
 $(BUILD)/programs.o: $(CBLOBS)
 
 # C programs also depend on the shared libc sources