move FPGA programming before overlay mount

Move FPGA programming from postBootCommands to preMount to ensure bitstream
is loaded before the filesystem becomes read-only. This fixes PL initialization
issues that occurred when the system booted in read-only mode.

flake.nix

@@ -442,7 +442,7 @@
                 (pkgs.python3.withPackages(ps: with ps; [ pyfastservo linien-server]))
                 fs-mode
               ];
-              boot.postBootCommands = lib.mkAfter ''
+              not-os.preMount = lib.mkAfter ''
 
                 # Program the FPGA
                 set +x

not-os-patches/pr-28.patch

@@ -59,7 +59,7 @@ index d7b0bf3..70353a1 100644
        '';
      }
 diff --git a/stage-1.nix b/stage-1.nix
-index 331fecd..f1f73cb 100644
+index 331fecd..67203ff 100644
 --- a/stage-1.nix
 +++ b/stage-1.nix
 @@ -117,11 +117,6 @@ let
@@ -96,8 +96,8 @@ index 331fecd..f1f73cb 100644
 +      mkdir -p /boot
 +      mount -t vfat -o ro /dev/mmcblk0p1 /boot
 +      USE_READONLY=1
-+      if [ -e /boot/rw_mode ]; then
-+        echo "Found rw_mode flag, enabling read-write mode"
++      if [ -e /boot/fs_mode_rw ]; then
++        echo "Found fs_mode_rw file, enabling read-write mode"
 +        USE_READONLY=0
 +      fi
 +      if [ "$USE_READONLY" = "1" ]; then