Fix the build after archiving rpg/ui/scene: drop their last live dependents

rpg/ui/scene moved to archive/ earlier left a handful of otherwise-generic
systems with dead references into them:
- asset/loader/chunk existed solely to load rpg overworld map chunks
  (tile_t, worldpos_t) - deleted outright, along with its
  ASSET_LOADER_TYPE_CHUNK entry in assetloader.c/h.
- save/slot wrapped party_t/storyflagval_t/map-name/cutscene-path, which is
  100% rpg save data - deleted outright (save.c/h, savedevice.c/h and the
  Linux save backend keep their generic settings/device-discovery logic,
  just lose the slot read/write pieces that only existed for it).
- locale/localemanager.c and test/CMakeLists.txt/test/save/* had a few
  stray includes and test cases that only existed for the now-gone code.

Also restores assets/locale/en_US.po (copied back from archive/assets/) -
locale init still needs a real locale file to boot into, even with the
asset-moving/archiving done separately.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

src/dusklinux/save/savedevicelinux.c

@@ -7,7 +7,6 @@
 
 #include "save/savedevice.h"
 #include "save/savedevicelinux.h"
-#include "save/slot/saveslot.h"
 #include "save/settings/savesettings.h"
 #include "save/savejson.h"
 #include "asset/asset.h"
@@ -86,92 +85,6 @@ errorret_t saveDeviceLinuxGetSettingsPath(
   errorOk();
 }
 
-errorret_t saveDeviceLinuxGetSlotPath(
-  char_t *dest,
-  const size_t destSize,
-  const uint8_t slotIndex
-) {
-  assertNotNull(dest, "dest cannot be null");
-
-  char_t directory[SAVE_DEVICE_LINUX_PATH_MAX];
-  errorChain(saveDeviceLinuxGetDirectory(directory, sizeof(directory)));
-
-  char_t filename[SAVE_SLOT_NAME_LENGTH + 16];
-  stringFormat(
-    filename, sizeof(filename) - 1,
-    SAVE_DEVICE_LINUX_SLOT_FILENAME_FORMAT, (uint32_t)slotIndex
-  );
-
-  stringFormat(dest, destSize, "%s/%s", directory, filename);
-  errorOk();
-}
-
-errorret_t saveDeviceLinuxSlotWrite(
-  savedevice_t *device,
-  saveslot_t *slot,
-  uint8_t slotIndex
-) {
-  assertNotNull(device, "device cannot be null");
-  assertNotNull(slot, "slot cannot be null");
-
-  char_t path[SAVE_DEVICE_LINUX_PATH_MAX];
-  errorChain(saveDeviceLinuxGetSlotPath(path, sizeof(path), slotIndex));
-
-  writeInit();
-
-  errorret_t writeResult = saveSlotWriteJSON(slot, doc, object);
-  if(errorIsNotOk(writeResult)) {
-    yyjson_mut_doc_free(doc);
-    errorChain(writeResult);
-  }
-
-  yyjson_write_err writeErr;
-  bool_t written = yyjson_mut_write_file(path, doc, 0, NULL, &writeErr);
-  yyjson_mut_doc_free(doc);
-
-  if(!written) {
-    errorThrow(
-      "Failed to write save slot file: %s (%s)", path, writeErr.msg
-    );
-  }
-
-  errorOk();
-}
-
-errorret_t saveDeviceLinuxSlotRead(
-  savedevice_t *device,
-  saveslot_t *slot,
-  uint8_t slotIndex
-) {
-  assertNotNull(device, "device cannot be null");
-  assertNotNull(slot, "slot cannot be null");
-
-  char_t path[SAVE_DEVICE_LINUX_PATH_MAX];
-  errorChain(saveDeviceLinuxGetSlotPath(path, sizeof(path), slotIndex));
-
-  yyjson_read_err readErr;
-  yyjson_doc *jsonDoc = yyjson_read_file(path, 0, NULL, &readErr);
-  if(jsonDoc == NULL) {
-    // No save file at this slot yet, leave the slot as-is.
-    if(readErr.code == YYJSON_READ_ERROR_FILE_OPEN) errorOk();
-    errorThrow(
-      "Failed to parse save slot file: %s (%s)", path, readErr.msg
-    );
-  }
-
-  yyjson_val *object = yyjson_doc_get_root(jsonDoc);
-  if(object == NULL) {
-    yyjson_doc_free(jsonDoc);
-    errorThrow("Save slot file missing root object: %s", path);
-  }
-
-  errorret_t readResult = saveSlotReadJSON(slot, object);
-  yyjson_doc_free(jsonDoc);
-  errorChain(readResult);
-
-  errorOk();
-}
-
 errorret_t saveDeviceLinuxSettingsWrite(
   savedevice_t *device,
   savesettings_t *settings