docs: give the FAQ console answer a command

The answer said --region us keeps only your region's BIOS, with nothing
to run. On the PlayStation it keeps 44 files, Japanese PS2 images among
them (install.py --system sony-playstation --region us --dry-run). The
answer now gives the --core command the installer itself suggests, in
the tabs of each system, and says what --region drops.

tests/test_site_wiki.py

@@ -426,6 +426,19 @@ def _entry(profile: dict, name: str) -> dict:
     raise AssertionError(f"{name} not in the profile")
 
 
+class TheFaqAnswersWithACommand(unittest.TestCase):
+    """"Do I need every file of a console?" answered `--region us keeps only
+    your region's BIOS`, with no command to run, and that run kept 44 files
+    of the PlayStation set, Japanese PS2 images among them. `--core pcsx1`
+    is the lever the installer itself names."""
+
+    def test_every_file_of_a_console(self):
+        section = _section(_wiki("faq.md"), "Do I need every file of a console?")
+        self.assertIn("<!-- os-tabs -->", section)
+        self.assertIn("--system sony-playstation --core pcsx1", section)
+        self.assertNotIn("only your region", section)
+
+
 class LegalOpensInPlainWords(unittest.TestCase):
     """C5: Is it legal? is a Start here page and opened on case law."""
 

wiki/faq.md

@@ -25,7 +25,14 @@ curl -fsSL https://abdess.github.io/retrobios/i | sh -s -- --dry-run
 
 ## Do I need every file of a console?
 
-No. `--region us` keeps only your region's BIOS.
+No. `--core` keeps what your emulator reads, here PCSX for PlayStation:
+
+<!-- os-tabs -->
+```sh
+curl -fsSL https://abdess.github.io/retrobios/i | sh -s -- --system sony-playstation --core pcsx1
+```
+
+`--region us` drops another region's BIOS where a US one exists.
 
 ## Does the BIOS set the game's language?