docs: readme installer options and plain wording

The quick install block gains the PowerShell form that passes options and a link to the installer page. The collection size uses the GB format of the download table and the site, counts get separators, and the sentences about RetroArch's existence check and the method describe the code instead of judging documentation.

tests/test_doc_pages.py

@@ -274,6 +274,7 @@ class PeerToneTowardPlatforms(unittest.TestCase):
         r"(?i)\bgets wrong\b|\bstale (hash|entries|entry)\b|<their file>|\bpatch their\b"
         r"|, corrected\b|\bcorrected in place\b|\bdeclare incorrectly\b|\blist error\b"
         r"|\btheir syntax\b|\bthe platform lacks\b|\bthe odd one\b|\bmay not match reality\b"
+        r"|\ball their code does\b|\bcan drift from\b"
     )
 
     def test_published_pages(self):
@@ -628,5 +629,44 @@ class ScratchFilesGoToRepoTmp(unittest.TestCase):
         self.assertIn("tmp/", (ROOT / ".gitignore").read_text(encoding="utf-8").splitlines())
 
 
+class ReadmeInstallerOptions(unittest.TestCase):
+    """The README named --system, --region and --check but showed options
+    only after `sh -s --`. Appended to `irm ... | iex`, PowerShell rejects
+    them, and the form that works was on the installer page alone, which the
+    README never linked."""
+
+    def test_quick_install_gives_the_powershell_form_and_the_page(self):
+        import generate_readme
+
+        source = inspect.getsource(generate_readme.generate_readme)
+        self.assertIn("&([scriptblock]::Create((irm https://raw.githubusercontent.com/Abdess/retrobios/main/install.ps1)))", source)
+        self.assertIn("wiki/installer/#passing-options", source)
+        self.assertIn("## Passing options", _page("installer.md"))
+        readme = (ROOT / "README.md").read_text(encoding="utf-8")
+        quick = _section(readme, "Quick install")
+        self.assertIn("[scriptblock]::Create", quick)
+        self.assertIn("wiki/installer/#passing-options", quick)
+        self.assertNotRegex(readme, r"(?m)^irm \S+ \| iex \S")
+
+
+class PublishedNumbersShareOneFormat(unittest.TestCase):
+    """The README gave the collection as `16011 MB` beside `19,526 files`,
+    the site home as 15.6 GB, and the emulators page `10095 files`."""
+
+    def test_generators_format_counts_and_sizes_alike(self):
+        import generate_readme
+        import generate_site
+
+        readme_source = inspect.getsource(generate_readme.generate_readme)
+        self.assertNotIn("size_mb", readme_source)
+        self.assertIn("format_size(total_size)", readme_source)
+        self.assertIn("{total_files:,}", inspect.getsource(generate_site))
+        self.assertEqual(generate_readme.format_size(16011 * 1024 * 1024), "15.6 GB")
+
+    def test_the_readme_has_no_bare_large_count(self):
+        readme = (ROOT / "README.md").read_text(encoding="utf-8")
+        self.assertEqual(re.findall(r"\*\*\d{4,}\b[^*]*\*\*", readme), [])
+
+
 if __name__ == "__main__":
     unittest.main()