Apply what might be the right translation to the CP/M boot tracks.

doc/disk-apple2.md

@@ -34,7 +34,7 @@ If you don't want an image in physical sector order, specify one of these option
 
   - `--appledos` Selects AppleDOS sector translation
   - `--prodos` Selects ProDOS sector translation
-  - `--cpm` Selects CP/M SoftCard sector translation[^1]
+  - `--cpm` Selects CP/M SoftCard sector translation[^1][^2]
 
 These options also select the appropriate file system; FluxEngine has read-only
 support for all of these. For example:
@@ -50,7 +50,10 @@ to 50 tracks, so it needs tweaking to support larger disks. FluxEngine doesn't
 understand these tweaks yet but they only become important when writing to
 disks, which isn't supported yet.
 
-[^1]: 80-track CP/M disks are interesting because all the tracks on the second
+[^1]: CP/M disks use the ProDOS translation for the first three tracks and a
+    different translation for all the tracks thereafter.
+
+[^2]: 80-track CP/M disks are interesting because all the tracks on the second
     side have on-disk track numbering from 80..159; the Apple II on-disk format
     doesn't have a side byte, so presumably this is to allow tracks on the two
     sides to be distinguished from each other. AppleDOS and ProDOS disks don't

src/formats/_apple2.textpb

@@ -138,6 +138,35 @@ option {
 
 		layout {
 			layoutdata {
+				# The boot tracks use ProDOS translation.
+
+				track: 0
+				up_to_track: 2
+				filesystem {
+					sector:  0
+					sector:  2
+					sector:  4
+					sector:  6
+					sector:  8
+					sector: 10
+					sector: 12
+					sector: 14
+					sector:  1
+					sector:  3
+					sector:  5
+					sector:  7
+					sector:  9
+					sector: 11
+					sector: 13
+					sector: 15
+				}
+			}
+
+			layoutdata {
+				# The data tracks use their own, special translation.
+
+				track: 3
+				up_to_track: 79
 				filesystem {
 					sector:  0
 					sector:  3