fix: every core ticked while none narrows the run

Cores drew every box empty when no core narrows the run, read as nothing
chosen. Every core is now drawn ticked, an untick keeps the others, All
and None work as on Choose systems, and the plan, Options and line mode
say all cores or N of M cores. A run with failures counts once, the
failed files said as failed.

tests/test_install_from.py

@@ -148,7 +148,7 @@ class CopyFromAnOldCard(FromFolder):
         proc = self.install()
         self.assertEqual(proc.returncode, 1, proc.stdout + proc.stderr)
         self.assertEqual(self.installed(), {"scph5500.bin": JP, "pcsx/extra.bin": EXTRA})
-        self.assertIn(f"2 files copied from {self.old}, 2 still missing.", proc.stdout)
+        self.assertIn(f"2 files copied from {self.old}, 2 failed.", proc.stdout)
 
     def test_a_link_out_of_the_folder_is_not_followed(self):
         outside = self.root / "elsewhere"
@@ -196,7 +196,7 @@ class CopyFromAnOldCard(FromFolder):
             (repo.root / "bios" / "mgba_extra.bin").unlink()
             proc = repo.run("--from", str(old), "--no-input")
             self.assertEqual(proc.returncode, 1, proc.stdout + proc.stderr)
-            self.assertIn(f"2 files copied from {old}, 2 downloaded, 1 still missing.",
+            self.assertIn(f"2 files copied from {old}, 2 downloaded, 1 failed.",
                           proc.stdout)
             self.assertEqual(sorted(repo.installed()), sorted(
                 name for name in payloads if name != "mgba/extra.bin"))