fix: say what minui and file-less cores get

--list-platforms said the MinUI layout was not written yet while
--from-pack and --dest wrote it. On the device the card root is now
found and its version.txt names the file list, and a card without one
gets the --platform and --dest to use. A core with no file of its own
says its files are the platform's, always kept, instead of 0 files.

tests/test_install.py

@@ -4727,8 +4727,28 @@ class HandheldSystemsByTheirOwnFiles(unittest.TestCase):
             {"/usr/trimui/": "", "/mnt/SDCARD/.system/res/": ""})
         self.assertEqual(found, [])
         self.assertIn("MinUI found here", err)
+        self.assertIn("--platform minui", err)
+        self.assertIn("--dest", err)
         self.assertNotIn("TrimUI", err)
 
+    def test_a_minui_card_on_its_device_gets_its_file_list(self):
+        """--list-platforms said the MinUI layout was not written yet, while
+        --from-pack and --dest wrote it: on the device the card root is the
+        folder, and the card's version.txt names which of the three it is."""
+        for release, plat, shown in (("MinUI-20251127-0", "minui", "MinUI"),
+                                     ("NextUI-20250601-1", "nextui", "NextUI"),
+                                     ("MyMinUI-20260809b-0", "myminui", "MyMinUI")):
+            with self.subTest(release=release):
+                root, found, name = self._one({
+                    "/usr/trimui/": "", "/mnt/SDCARD/.system/res/": "",
+                    "/mnt/SDCARD/.system/version.txt": release + "\n"})
+                self.assertEqual((found, name), ((plat, root / "mnt/SDCARD"), shown))
+
+    def test_the_listing_says_what_the_minui_family_gets(self):
+        line = next(line for line in install._system_lines() if line.startswith("MinUI:"))
+        self.assertNotIn("does not write", line)
+        self.assertIn("minui, nextui or myminui", line)
+
     def test_two_unrelated_systems_are_refused(self):
         _root, found, names, _err = self._found(
             {"/mnt/SDCARD/Koriki/version.txt": "1\n"}, 'OS_NAME="JELOS"\n')

tests/test_install_selection.py

@@ -9,6 +9,7 @@ to one answer.
 
 from __future__ import annotations
 
+import contextlib
 import functools
 import hashlib
 import http.server
@@ -353,6 +354,42 @@ class CommandLineChoices(unittest.TestCase):
                 install.parse_selection(bad, 5)
 
 
+class ACoreWithNoFileOfItsOwn(unittest.TestCase):
+    """pcsx_rearmed, swanstation and pcsx1 showed `0 files, 0 B` in the
+    cores step and in --list-cores, which reads as "this core gets nothing":
+    their files are the platform's own, which are always kept."""
+
+    FILES = [
+        {"dest": "scph5501.bin", "size": 5, "cores": None, "systems": ["sony-playstation"],
+         "declared_choices": [], "slot_choices": [{"cores": ["pcsx_rearmed"]}]},
+        {"dest": "ps2.bin", "size": 9, "cores": ["duckstation"],
+         "systems": ["sony-playstation"]},
+    ]
+
+    def _line(self, out: str, core: str) -> str:
+        return next(line for line in out.splitlines() if line.strip().startswith(core)
+                    or f") {core}" in line)
+
+    def test_the_listing_says_its_files_are_the_platforms(self):
+        out = io.StringIO()
+        with contextlib.redirect_stdout(out):
+            install._print_choices("retroarch", self.FILES, [], systems=False)
+        line = self._line(out.getvalue(), "pcsx_rearmed")
+        self.assertNotIn("0 files", line)
+        self.assertIn("always kept", line)
+        self.assertIn("1 file, 9 B", self._line(out.getvalue(), "duckstation"))
+
+    def test_the_cores_step_says_so_too(self):
+        answers = iter(["c", "", ""])
+        out = io.StringIO()
+        with mock.patch("builtins.input", lambda _prompt="": next(answers)), \
+                contextlib.redirect_stdout(out):
+            install._prompt_custom_selection("retroarch", self.FILES, [])
+        line = self._line(out.getvalue(), "pcsx_rearmed")
+        self.assertNotIn("0 files", line)
+        self.assertIn("always kept", line)
+
+
 class TheBoundaryChecksTheNewFields(unittest.TestCase):
     def _manifest(self, **extra):
         entry = {"dest": "a.bin", "sha1": "a" * 40, "size": 1,