Add compressed combined save format for PSP and Dolphin

Memory sticks/cards don't suit N+1 separate save files the way Linux's
filesystem does, so add an opt-in SAVE_DEVICE_DATA_RAW mode: settings and
all save slots get serialized to JSON, concatenated, zlib-compressed, and
framed with a magic/version/checksum/generation header, then read/written
as a single blob through one combined platform hook instead of four.

- PSP and Dolphin's SD/NAND backends write via a temp file + atomic rename,
  so a crash mid-write can never leave a half-written save behind.
- GameCube memory cards have no rename or resize primitive, so they
  ping-pong between two fixed files instead, picking whichever is valid and
  has the higher generation counter on load.
- Linux is untouched (still four separate JSON files); saveslot.h/
  savesettings.h drop their now-unnecessary pack(1) now that nothing
  persists them as raw bytes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/duskdolphin/save/savedeviceplatform.h

@@ -25,6 +25,12 @@
   #define saveDeviceCheckAvailabilityPlatform \
     saveDeviceDolphinNandCheckAvailability
   #define saveDevicePlatformDispose saveDeviceDolphinNandDispose
+
+  // ISFS_Rename exists, so NAND uses the same write-temp-then-rename
+  // pattern as PSP/Linux - see SAVE_DEVICE_DATA_RAW in save/savedevice.h.
+  #define SAVE_DEVICE_DATA_RAW
+  #define saveDeviceDataWritePlatform saveDeviceDolphinNandDataWrite
+  #define saveDeviceDataReadPlatform saveDeviceDolphinNandDataRead
 #elif defined(DUSK_WII) && defined(DUSK_SAVE_WII_METHOD_SD)
   #include "savedevicedolphinsd.h"
   #define SAVE_DEVICE_COUNT 1
@@ -33,6 +39,13 @@
   #define saveDeviceCheckAvailabilityPlatform \
     saveDeviceDolphinSDCheckAvailability
   #define saveDevicePlatformDispose saveDeviceDolphinSDDispose
+
+  // libfat gives standard POSIX rename(), so SD uses the same
+  // write-temp-then-rename pattern as PSP/Linux - see SAVE_DEVICE_DATA_RAW
+  // in save/savedevice.h.
+  #define SAVE_DEVICE_DATA_RAW
+  #define saveDeviceDataWritePlatform saveDeviceDolphinSDDataWrite
+  #define saveDeviceDataReadPlatform saveDeviceDolphinSDDataRead
 #else
   #include "savedevicedolphincard.h"
   #define SAVE_DEVICE_COUNT 2
@@ -41,4 +54,11 @@
   #define saveDeviceCheckAvailabilityPlatform \
     saveDeviceDolphinCardCheckAvailability
   #define saveDevicePlatformDispose saveDeviceDolphinCardDispose
+
+  // No rename or resize primitive on the CARD API, so this ping-pongs
+  // between two fixed files instead - see SAVE_DEVICE_DOLPHIN_CARD_FILENAME_0
+  // in savedevicedolphincard.h and SAVE_DEVICE_DATA_RAW in save/savedevice.h.
+  #define SAVE_DEVICE_DATA_RAW
+  #define saveDeviceDataWritePlatform saveDeviceDolphinCardDataWrite
+  #define saveDeviceDataReadPlatform saveDeviceDolphinCardDataRead
 #endif