fs rewrite stage 2: inodes + root directory (block-based, persistent)

- fs.asm: a real block filesystem on the persistent block device - superblock,
  block/inode bitmaps, a 32-entry inode table (type, size, 8 direct block
  pointers -> files up to 2 KiB), and a root directory of 16-byte entries.
  Metadata cached in WRAMX; one-block data cache streams file/dir blocks.
- same syscall interface (open/getb/putb/list/remove) -> tools unchanged;
  ls now enumerates until flist() runs out (16 files, was hardcoded 8).
- old 8-slot WRAM FS removed; cart RAM partitioned: process banks 0-7, disk 8-11.
- two register-clobber bugs fixed: alloc_block/alloc_inode returned the
  bitmap-block number (write_bitmap clobbers C); db_use loaded the wrong block
  on a transition (db_flush->write_block clobbers C) -> multi-block files broke.
- verified: 10+ files, multi-block (300-byte) files, delete, and persistence
  across reboots. Debug 'blk' disk tool retained (fill/peek).
- README: document the block filesystem.

1 files changed, 1 insertions, 0 deletions

diff --git a/c/gbos.h b/c/gbos.h
index 03a91de..6badd16 100644
--- a/c/gbos.h
+++ b/c/gbos.h
@@ -45,4 +45,5 @@ void          yield(void);
 unsigned char reap(void);                   /* reap a finished bg job, or 0   */
 void          bfill(unsigned char block, unsigned char byte); /* [debug] disk */
 unsigned char bpeek(unsigned char block);                     /* [debug] disk */
+unsigned char bpeek2(unsigned char block, unsigned char off);
 #endif