fat: mount every FAT32 volume under /disk/<UID>/, fix multi-entry LFN

- fat.rs: VOL: Option<Volume> → VOLS: Vec<Volume>; try_mount() returns
  a Volume per disk and init() mounts every valid FAT32 volume found.
  Volume UID = sanitized uppercase label + 8-hex volume serial
  (e.g. RSDOS-5BD1E55F): unique per format, stable across reboots,
  human-recognizable, machine-parseable (^[A-Z0-9_]+-[0-9A-F]{8}$);
  cloned volumes get a -N suffix.  Public ops take a vol index and
  select it (select_vol also picks the backing AHCI disk), matching
  the ahci::select pattern
- fs.rs: /disk is now a plain directory whose children are one Disk
  node per mounted volume, named by UID; DiskInfo carries vol
- LFN fix: entries are stored last-first on disk — both the writer
  (head-entry first) and reader (append in disk order) were reversed
  and cancelled out for ≤13-char names; multi-entry names (>13 chars)
  read back mangled (e.g. 'from-kernel.txt' as 'xt').  Writer now
  places seq=1 closest to the SFN and seq=N|0x40 first; reader places
  chunks by sequence number and trims at the first NUL.  Verified with
  a 25-char filename round trip: kernel ls/cat correct, mtools shows
  the full LFN, fsck clean on both volumes
- test-disk.sh: test file renamed to disk-test-.txt (>13 chars,
  exercises multi-entry LFN); UID discovered from the boot log; QEMU
  stdio redirected to a log file + EXIT trap so an orphaned QEMU can
  never hang a piped caller (it previously did, 400s)

2 files changed, 30 insertions, 13 deletions

diff --git a/scripts/mkdisk.sh b/scripts/mkdisk.sh
index f9a8c09..6bdd50c 100755
--- a/scripts/mkdisk.sh
+++ b/scripts/mkdisk.sh
@@ -55,10 +55,10 @@ fi
 
 # mkfs.fat sizes are 1024-byte blocks; accept M/G/K suffixes too.
 case "$SIZE" in
-*G) SIZE_BLOCKS=$(( ${SIZE%G} * 1024 * 1024 )) ;;
-*M) SIZE_BLOCKS=$(( ${SIZE%M} * 1024 )) ;;
-*K) SIZE_BLOCKS=$(( ${SIZE%K} )) ;;
-*)      SIZE_BLOCKS="$SIZE" ;;
+*G) SIZE_BLOCKS=$((${SIZE%G} * 1024 * 1024)) ;;
+*M) SIZE_BLOCKS=$((${SIZE%M} * 1024)) ;;
+*K) SIZE_BLOCKS=$((${SIZE%K})) ;;
+*) SIZE_BLOCKS="$SIZE" ;;
 esac
 if [ -z "$SIZE_BLOCKS" ] || [ "$SIZE_BLOCKS" -le 0 ] 2>/dev/null; then
         echo "mkdisk: bad size '$SIZE' (use e.g. 64M or 65536)" >&2
diff --git a/scripts/test-disk.sh b/scripts/test-disk.sh
index f7be7c6..f7337ef 100755
--- a/scripts/test-disk.sh
+++ b/scripts/test-disk.sh
@@ -31,8 +31,13 @@ ESP_DIR="$PROJECT_DIR/esp"
 QPID=/tmp/rsdos-test-qpid
 SOCK=/tmp/rsdos-test-qmon.sock
 LOG=/tmp/rsdos-test-serial.log
+QLOG=/tmp/rsdos-test-qemu.log
 STAMP="$(date +%s)"
 
+# Never leave a QEMU behind (an orphan holding our stdout would hang any
+# caller that pipes our output).
+trap 'kill "$(cat "$QPID" 2>/dev/null)" 2>/dev/null || true' EXIT
+
 fail() {
         echo "FAIL: $1"
         [ -f "$LOG" ] && tail -20 "$LOG"
@@ -42,7 +47,7 @@ fail() {
 # wait_log FILE PATTERN TIMEOUT-SECONDS — poll a file for a regex.
 wait_log() {
         local i=0
-        while [ "$i" -lt $(( ${3:-60} * 10 )) ]; do
+        while [ "$i" -lt $((${3:-60} * 10)) ]; do
                 grep -q "$2" "$1" 2>/dev/null && return 0
                 sleep 0.1
                 i=$((i + 1))
@@ -53,7 +58,7 @@ wait_log() {
 # wait_qemu_exit TIMEOUT-SECONDS — poll until the pid is gone.
 wait_qemu_exit() {
         local i=0
-        while [ "$i" -lt $(( ${1:-30} * 10 )) ]; do
+        while [ "$i" -lt $((${1:-30} * 10)) ]; do
                 kill -0 "$(cat "$QPID" 2>/dev/null)" 2>/dev/null || return 0
                 sleep 0.1
                 i=$((i + 1))
@@ -80,18 +85,29 @@ rm -f "$SOCK" "$LOG"
         -device ide-hd,drive=esp,bus=ide.1 \
         -serial file:"$LOG" \
         -monitor unix:"$SOCK",server,nowait \
-        -m 256M -machine q35 -cpu qemu64 -no-reboot -display none &
-echo $! > "$QPID"
+        -m 256M -machine q35 -cpu qemu64 -no-reboot -display none \
+        >"$QLOG" 2>&1 &
+echo $! >"$QPID"
 
 wait_log "$LOG" "boot: entering shell" 90 || fail "kernel never reached the shell"
 sleep 1
 
+# Volumes mount under /disk/<UID>/ where UID = "LABEL-SERIAL" (e.g.
+# RSDOS-5BD1E55F).  Discover it from the boot log so the test works on
+# any image without knowing the serial in advance.
+VOL_UID="$(grep -a 'fat: mounted' "$LOG" | sed -n 's/.*at \/disk\/\([^ )]*\).*/\1/p' | head -1)"
+[ -n "$VOL_UID" ] || fail "no FAT32 volume was mounted (look for 'fat: mounted' in the log)"
+echo "  mounted volume UID: $VOL_UID"
+
 echo "==> 4/6 drive the shell (ls / mkdir / echo > / cat / poweroff)"
+# The filename is deliberately >13 chars so the FAT LFN path gets
+# multi-entry entries (they're stored last-first on disk).
+TESTFILE="disk-test-$STAMP.txt"
 python3 "$SCRIPT_DIR/sendkeys.py" --sock "$SOCK" \
         "ls /disk" \
-        "mkdir /disk/sub" \
-        "echo disk-test-$STAMP > /disk/sub/hello.txt" \
-        "cat /disk/sub/hello.txt" \
+        "mkdir /disk/$VOL_UID/sub" \
+        "echo disk-test-$STAMP > /disk/$VOL_UID/sub/$TESTFILE" \
+        "cat /disk/$VOL_UID/sub/$TESTFILE" \
         "poweroff"
 
 echo "==> 5/6 wait for shutdown"
@@ -102,10 +118,11 @@ grep -a "disk-test-$STAMP" "$LOG" >/dev/null || fail "cat output missing from se
 if ! fsck.fat -n "$IMG" >/tmp/rsdos-fsck.out 2>&1; then
         fail "fsck.fat reports problems: $(cat /tmp/rsdos-fsck.out | tail -3)"
 fi
-MT="$(mtype -i "$IMG" "::/sub/hello.txt" 2>/dev/null || true)"
+MT="$(mtype -i "$IMG" "::/sub/$TESTFILE" 2>/dev/null || true)"
 [ "$MT" = "disk-test-$STAMP" ] || fail "mtype mismatch: got '$MT'"
 
 echo ""
 echo "PASS — disk round trip OK (fsck clean, file survived poweroff)"
 echo "  image:      $IMG"
-echo "  written:    /disk/sub/hello.txt = \"disk-test-$STAMP\""
+echo "  volume:     /disk/$VOL_UID"
+echo "  written:    /disk/$VOL_UID/sub/$TESTFILE = \"disk-test-$STAMP\""