BuhBye: Cycle through volumes after the boot volume more intuitively

Previously, the boot volume was shown first, but then tab would cycle
from the highest priority volume to the lowest. This would be awkward
if the boot volume was not the highest priority volume. For example,
with these devices (listed lowest to highest priority, like DEVLST),
/HD1 is the boot volume but the RAM disks are highest priority:

(low) /FLOPPY2 /FLOPPY1 /HD4 /HD3 /HD2 /HD1 /RAMWORKS /RAM (high)

Prior to this fix, it would cycle:

/HD1 /RAM /RAMWORKS /HD1 /HD2 /HD3 /HD4 /FLOPPY1 /FLOPPY2 /RAM ...

After this fix, it will cycle:

/HD1 /HD2 /HD3 /HD4 /FLOPPY1 /FLOPPY2 /RAM /RAMWORKS /HD1 ...

To fit, a little bit of code golfing was necessary.

selectors/buhbye.system.s

@@ -100,7 +100,7 @@ loop:   lda     (src_ptr)       ; *src_ptr = *dst_ptr
         read_buffer     := $2000 ; Also, start location for launched SYS files
 
         ;; Device/Prefix enumeration
-        next_device_num := $65  ; next device number to try
+        cur_device_num  := $65  ; device number to try
         prefix_depth    := $6B  ; 0 = root
 
         ;; Directory enumeration
@@ -146,22 +146,23 @@ loop:   lda     (src_ptr)       ; *src_ptr = *dst_ptr
         sta     BITMAP
 
         ;; Find device
-        lda     DEVCNT          ; max device num
-        sta     next_device_num
-        lda     DEVNUM
-        bne     check_device
+        ldx     DEVCNT
+:       lda     DEVLST,x
+        and     #%11110000
+        cmp     DEVNUM
+        beq     check_device
+        dex
+        bra     :-
 
 next_device:
-        ldx     next_device_num
-        lda     DEVLST,x
-        cpx     #1
-        bcs     :+
+        ldx     cur_device_num
+        dex
+        bpl     :+
         ldx     DEVCNT
-        inx
-:       dex
-        stx     next_device_num
+:       lda     DEVLST,x
 
 check_device:
+        stx     cur_device_num
         sta     on_line_params_unit
         MLI_CALL ON_LINE, on_line_params
         bcs     next_device
@@ -256,9 +257,9 @@ store_entry:
         sta     (curr_ptr),y
         dey
         bpl     :-
-        iny                     ; Y = 0; storage_type/name_length in A
+                                ; storage_type/name_length in A
         and     #%00001111      ; mask off name_length (remove storage_type)
-        sta     (curr_ptr),y    ; store length
+        sta     (curr_ptr)      ; store length
 
         inc     num_entries
 
@@ -300,9 +301,9 @@ next_in_block:
         lda     entry_pointer
         adc     entry_length
         sta     entry_pointer
-        lda     entry_pointer+1
-        adc     #0
-        sta     entry_pointer+1
+        bcc     :+
+        inc     entry_pointer+1
+:
 
         inc     block_entries
 
@@ -568,9 +569,9 @@ loop:   lda     help_string,y
         clc
         adc     curr_ptr+1
         sta     curr_ptr+1
-        ldy     #0
-        lda     (curr_ptr),y
+        lda     (curr_ptr)
         sta     curr_len
+        ldy     #0              ; needed by caller
         ;; fall through
 .endproc
 
@@ -691,7 +692,7 @@ cout:   jmp     COUT
 ;;; ------------------------------------------------------------
 
 .endproc
-        .assert .sizeof(selector) <= max_size, error, "Must fit in $300 bytes"
+        .assert .sizeof(selector) <= max_size, error, .sprintf("Must fit in $300 bytes, is: $%x", .sizeof(selector))
         install_size = .sizeof(selector)
         poporg