chore: one folder per console

DS and DSi split into Nintendo DS and Nintendo DSi. 64DD, Mega-CD,
ZXSpectrum, VSmile, BBC and Game Engines/DOOM merge into the folder
of the same console. Same-named dumps with other bytes are kept:
BBC Micro's earlier zips in .variants/, the vsmilem set in vsmilem/,
the Doom II 1.666 IWAD in v1.666/, BizHawk's DSi firmware in bizhawk/.
Galaksija and Vircon get a console folder, sdlpal's desc.dat joins
its tree, VICE's PET and CBM-II ROMs leave C128 with their vice/ tail.

Database and manifests regenerated together. Verify and cross
reference give the same result once moved paths are mapped.

tests/test_site_r3_collection.py

@@ -0,0 +1,63 @@
+"""One folder per console.
+
+A system section is named after the folder its files live in. Nintendo held
+DS and Nintendo DS, 64DD and Nintendo 64DD, Sega held Mega CD and Mega-CD,
+Sinclair ZX Spectrum and ZXSpectrum, VTech V.Smile and VSmile, Acorn BBC and
+BBC Micro: each console had two sections that hid each other on the site.
+Reads the git index, which is what a clone checks out.
+"""
+
+from __future__ import annotations
+
+import re
+import subprocess
+import unittest
+from collections import defaultdict
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+
+
+def console_key(name: str) -> str:
+    return re.sub(r"[\s.\-]", "", name).casefold()
+
+
+def twin_consoles(paths: list[str]) -> list[list[str]]:
+    """Console folders of one maker that read as the same name."""
+    spellings: dict[tuple[str, str], set[str]] = defaultdict(set)
+    for path in paths:
+        parts = path.split("/")
+        if len(parts) < 4 or parts[0] != "bios":
+            continue
+        maker, console = parts[1], parts[2]
+        spellings[(maker, console_key(console))].add(f"{maker}/{console}")
+    return sorted(sorted(names) for names in spellings.values() if len(names) > 1)
+
+
+class OneFolderPerConsole(unittest.TestCase):
+    def test_no_maker_files_one_console_twice(self) -> None:
+        listed = subprocess.run(
+            ["git", "ls-files", "-z", "--", "bios"],
+            cwd=REPO_ROOT, capture_output=True, text=True,
+        )
+        if listed.returncode != 0 or not listed.stdout:
+            self.skipTest("not a git checkout with bios/")
+        paths = [p for p in listed.stdout.split("\0") if p]
+        self.assertEqual(twin_consoles(paths), [])
+
+    def test_spaces_dashes_and_dots_do_not_make_a_new_console(self) -> None:
+        self.assertEqual(
+            twin_consoles([
+                "bios/Sega/Mega CD/a.bin",
+                "bios/Sega/Mega-CD/b.bin",
+                "bios/VTech/V.Smile/c.bin",
+                "bios/VTech/VSmile/d.bin",
+                "bios/Atari/Lynx/e.bin",
+                "bios/Camputers/Lynx/f.bin",
+            ]),
+            [["Sega/Mega CD", "Sega/Mega-CD"], ["VTech/V.Smile", "VTech/VSmile"]],
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()