docs: point users to --check and exact pack files

Troubleshooting, the FAQ and the download page sent people who only ran
the installer to verify.py, which reads the repository, not their BIOS
folder. Download links now name the exact asset of the recorded release,
the --dest example names the BIOS folder on the card, the slice layout
left with the last release that used it, and the shown verify output is
what the tool prints.

tests/test_split_pack.py

@@ -212,13 +212,12 @@ class PartsAreExplainedWhereTheyAreDownloaded(unittest.TestCase):
     def _text(self, relative: str) -> str:
         return (REPO_ROOT / relative).read_text(encoding="utf-8")
 
-    def test_every_page_names_both_layouts(self):
-        """The older release stays downloadable until the next one replaces it."""
+    def test_every_page_names_the_parts(self):
+        """Slices left the pages with the last release that used them
+        (test_doc_surfaces.SlicesLeaveWithTheirRelease)."""
         for page in self.PAGES:
             with self.subTest(page=page):
-                text = self._text(page)
-                self.assertTrue(".part1of2.zip" in text)
-                self.assertTrue(".zip.001" in text)
+                self.assertIn(".part1of2.zip", self._text(page))
 
     def test_the_windows_join_command_runs_from_powershell(self):
         """`copy /b A+B C` is a cmd builtin. Typed into PowerShell, the shell