Fixed a bunch of code inconsistencies

src/duskdolphin/save/savedevicedolphincard.h

@@ -97,6 +97,33 @@ bool_t saveDeviceDolphinCardHasFreeSpace(const int32_t channel);
  */
 errorret_t saveDeviceDolphinCardDispose(savedevice_t *device);
 
+// One probe result for one of the two ping-pong slots.
+typedef struct {
+  bool_t valid;
+  uint32_t generation;
+  uint8_t *buffer;// only set if keepBuffer was requested, else NULL
+  uint32_t len;
+} savedevicedolphincardslot_t;
+
+/**
+ * Opens the given card file (if it exists) and validates it as a raw save
+ * blob via saveDeviceRawIsValid(). CARD_Read requires a 32-byte aligned
+ * buffer, so the read (and any buffer kept for the caller) uses memoryAlign
+ * rather than memoryAllocate. If keepBuffer is false, or the file doesn't
+ * exist/validate, no buffer is left allocated.
+ *
+ * @param channel The CARD slot (CARD_SLOTA or CARD_SLOTB) to probe.
+ * @param filename The card file name to open.
+ * @param keepBuffer Whether to keep the read buffer allocated on success.
+ * @return The probe result - valid is false if the file doesn't exist or
+ *   doesn't validate as a raw save blob.
+ */
+savedevicedolphincardslot_t saveDeviceDolphinCardProbeSlot(
+  const int32_t channel,
+  const char_t *filename,
+  const bool_t keepBuffer
+);
+
 /**
  * Writes the combined save data blob out to whichever of the two fixed
  * card files (see SAVE_DEVICE_DOLPHIN_CARD_FILENAME_0/1 above) is not