fix: drop np2kai font.rom, a fallback of FONT.ROM

The np2kai shared group declared font.rom as a second required file
while NP2kai reads it only when FONT.ROM, which System.dat already
declares, is absent. Case-sensitive platforms packed the font twice.
A shared group may now add a second spelling only where some code
opens that spelling itself, as the two rhythm engines do.

platforms/_shared.yml

@@ -40,6 +40,8 @@ shared_groups:
   # NEC PC-9801/9821 — NP2kai core
   # np2kai hardcodes "np2kai/" subfolder for firmware lookups
   # ref: NP2kai/sdl/libretro/libretro.c:1804,1806 — milstr_ncat(np2path, "/np2kai")
+  # font.rom is the lowercase fallback for FONT.ROM, which System.dat declares
+  # (font/font.c:192-195): an alias in the profile, not a second file here.
   np2kai:
     - name: bios.rom
       destination: np2kai/bios.rom
@@ -48,13 +50,6 @@ shared_groups:
       md5: "cd237e16e7e77c06bb58540e9e9fca68"
       crc32: "0a682b93"
       size: 98304
-    - name: font.rom
-      destination: np2kai/font.rom
-      required: true
-      sha1: "78ba9960f135372825ab7244b5e4e73a810002ff"
-      md5: "38d32748ae49d1815b0614970849fd40"
-      crc32: "456d9fc7"
-      size: 288768
     - name: itf.rom
       destination: np2kai/itf.rom
       required: true

tests/test_no_case_collisions.py

@@ -54,5 +54,53 @@ class TestNoCaseCollisions(unittest.TestCase):
         )
 
 
+class SharedGroupsAddNoSecondSpelling(unittest.TestCase):
+    """The np2kai group added np2kai/font.rom beside System.dat's
+    np2kai/FONT.ROM. NP2kai reads font.rom only when FONT.ROM is absent: an
+    alternative name, which belongs in the profile's aliases. On Lakka and
+    RetroPie, whose filesystems keep both, the pack carried the font twice
+    and verify counted one more required file."""
+
+    def test_no_group_entry_respells_a_declared_destination(self) -> None:
+        import sys
+
+        sys.path.insert(0, str(REPO_ROOT / "scripts"))
+        from common import (
+            list_registered_platforms,
+            load_emulator_profiles,
+            load_platform_config,
+        )
+
+        # A spelling some code opens as its own file stands: NP2kai's rhythm
+        # engine reads 2608_bd.wav, its fmgen engine 2608_BD.WAV, and a
+        # case-sensitive filesystem needs both. A spelling that is only ever
+        # an alias is the same file asked for twice.
+        read_as_named = {
+            str(entry.get("path") or entry.get("name") or "")
+            for profile in load_emulator_profiles(str(REPO_ROOT / "emulators")).values()
+            for entry in profile.get("files", [])
+            if isinstance(entry, dict)
+        }
+        platforms_dir = str(REPO_ROOT / "platforms")
+        respelled: list[str] = []
+        for name in list_registered_platforms(platforms_dir, include_archived=True):
+            config = load_platform_config(name, platforms_dir)
+            own: dict[str, str] = {}
+            grouped: list[tuple[str, str]] = []
+            for system in config.get("systems", {}).values():
+                for entry in system.get("files", []):
+                    dest = entry.get("destination") or entry.get("name") or ""
+                    if entry.get("shared_group"):
+                        grouped.append((dest, entry["shared_group"]))
+                    else:
+                        own.setdefault(dest.casefold(), dest)
+            for dest, group in grouped:
+                spelled = own.get(dest.casefold())
+                named = dest in read_as_named
+                if spelled and spelled != dest and not named:
+                    respelled.append(f"{name}: {group} adds {dest} beside {spelled}")
+        self.assertEqual(respelled, [])
+
+
 if __name__ == "__main__":
     unittest.main()