fix pi-lens warnings: unwraps, shell SC2046, dup code (fmtbuf/scripts/hexdump/cat/ahci/pci)

- memory.rs: self-test Layout::from_size_align no longer panics — the
  test fails cleanly on an invalid layout
- fat.rs: v() no longer unwraps the active-volume slot — invariant
  violation logs + halts instead of panicking mid-disk-io
- strbuf: shared FmtBuf replaces the duplicated PanicBuf/FmtBuf
  (main.rs + sched.rs)
- test-disk.sh: SC2046 — conditional --fresh arg no longer relies on
  word splitting
- scripts: boot.sh/boot-image.sh share lib-boot-args.sh (dup args loop)
- shell: cat/hexdump stdin pairs unified with Option<&str> marker;
  hexdump format_row folded into format_partial
- ahci: read/write_sectors unified behind dma_sectors
- pci: config_read/write share config_addr

4 files changed, 50 insertions, 41 deletions

diff --git a/scripts/boot-image.sh b/scripts/boot-image.sh
index 913e5cb..e8c093c 100755
--- a/scripts/boot-image.sh
+++ b/scripts/boot-image.sh
@@ -34,29 +34,8 @@ GUI=""
 DEBUG=""
 
 # ---- args ----
-while [ $# -gt 0 ]; do
-        case "$1" in
-        --gui | -g) GUI="-vga std" ;;
-        --debug | -d) DEBUG="-s -S" ;;
-        --mem)
-                shift
-                MEM="$1"
-                ;;
-        --smp)
-                shift
-                SMP="$1"
-                ;;
-        --help | -h)
-                head -20 "$0" | grep "^#" | sed 's/^# //'
-                exit 0
-                ;;
-        *)
-                echo "unknown: $1"
-                exit 1
-                ;;
-        esac
-        shift
-done
+source "$SCRIPT_DIR/lib-boot-args.sh"
+parse_boot_args "$@"
 
 # ---- build image if missing ----
 if [ ! -f "$IMAGE" ]; then
diff --git a/scripts/boot.sh b/scripts/boot.sh
index 99fd103..5b8e6fa 100755
--- a/scripts/boot.sh
+++ b/scripts/boot.sh
@@ -45,33 +45,21 @@ GUI=""
 DEBUG=""
 
 # ---- args ----
-while [ $# -gt 0 ]; do
+source "$SCRIPT_DIR/lib-boot-args.sh"
+# boot.sh-specific flags live here; everything else is shared.
+handle_arg() {
         case "$1" in
-        --gui | -g) GUI="-vga std" ;;
-        --debug | -d) DEBUG="-s -S" ;;
         --release | -r)
                 PROFILE="release"
                 CARGO_FLAGS="--release"
                 ;;
-        --mem)
-                shift
-                MEM="$1"
-                ;;
-        --smp)
-                shift
-                SMP="$1"
-                ;;
-        --help | -h)
-                head -20 "$0" | grep "^#" | sed 's/^# //'
-                exit 0
-                ;;
         *)
                 echo "unknown: $1"
                 exit 1
                 ;;
         esac
-        shift
-done
+}
+parse_boot_args "$@"
 
 OUT_DIR="target/x86_64-unknown-uefi/$PROFILE"
 KERNEL="$OUT_DIR/rsdos.efi"
diff --git a/scripts/lib-boot-args.sh b/scripts/lib-boot-args.sh
new file mode 100644
index 0000000..ec97500
--- /dev/null
+++ b/scripts/lib-boot-args.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+#
+# scripts/lib-boot-args.sh — shared CLI parsing for the QEMU boot scripts.
+# Sourced, not executed.  The caller sets default values for GUI/DEBUG/
+# MEM/SMP first, then calls `parse_boot_args "$@"`.  A caller with extra
+# flags defines its own `handle_arg()` to intercept them before the
+# shared cases run (unknown args still fail loudly).
+set -euo pipefail
+
+parse_boot_args() {
+        while [ $# -gt 0 ]; do
+                case "$1" in
+                --gui | -g) GUI="-vga std" ;;
+                --debug | -d) DEBUG="-s -S" ;;
+                --mem)
+                        shift
+                        MEM="$1"
+                        ;;
+                --smp)
+                        shift
+                        SMP="$1"
+                        ;;
+                --help | -h)
+                        head -20 "$0" | grep "^#" | sed 's/^# //'
+                        exit 0
+                        ;;
+                *) handle_arg "$1" ;;
+                esac
+                shift
+        done
+}
+
+# Default: no extra flags.  A script with more defines its own before
+# calling parse_boot_args.
+handle_arg() {
+        echo "unknown: $1"
+        exit 1
+}
diff --git a/scripts/test-disk.sh b/scripts/test-disk.sh
index 11a9b05..0268fff 100755
--- a/scripts/test-disk.sh
+++ b/scripts/test-disk.sh
@@ -72,7 +72,11 @@ cargo build --package rsdos --target x86_64-unknown-uefi
 echo "==> 2/6 deploy to ESP + ensure disk image"
 mkdir -p "$ESP_DIR/EFI/BOOT"
 cp target/x86_64-unknown-uefi/debug/rsdos.efi "$ESP_DIR/EFI/BOOT/BOOTX64.EFI"
-"$SCRIPT_DIR/mkdisk.sh" $([ "$FRESH" -eq 1 ] && echo --fresh) "$IMG"
+if [ "$FRESH" -eq 1 ]; then
+        "$SCRIPT_DIR/mkdisk.sh" --fresh "$IMG"
+else
+        "$SCRIPT_DIR/mkdisk.sh" "$IMG"
+fi
 
 echo "==> 3/6 boot QEMU (headless)"
 kill "$(cat "$QPID" 2>/dev/null)" 2>/dev/null || true