fix: offer Lakka's card route from Linux only

Lakka keeps /storage on the card's ext4 partition (Lakka-LibreELEC
4696b48f scripts/mkimage:72, 95), which Windows and macOS do not open, and
its page offered them a card route. card_run is now [linux], and a page
with no Windows route says only Linux opens the card.

platforms/_guides.yml

@@ -452,6 +452,9 @@ guides:
       Turn on **SSH**, a terminal over the network, in Lakka's **Settings > Services**. From
       a computer, connect with `ssh root@lakka`, password `root`. Paste the line. Press
       Enter.
+    # /storage is the card's ext4 partition, the other one FAT32 (Lakka-LibreELEC
+    # 4696b48f, scripts/mkimage:71-72 and 95): from a computer, only Linux opens it.
+    card_run: [linux]
     reference_notes:
     - The folder is reachable over SSH and over the network share.
     pack_manual: |
@@ -648,8 +651,7 @@ guides:
       RetroPie also installs standalone emulators (openMSX, PCSX2, XRoar, Amiberry and
       others) whose files only the RetroPie file list carries.
     - >-
-      RetroPie is archived in this project: the command serves it, and checks that cover
-      every setup include it only on request.
+      RetroPie is archived here: checks of every setup include it only on request.
     pack_manual: |
       Option B: Via network share
       --------------------------

scripts/generate_site.py

@@ -4188,7 +4188,11 @@ def _card_route(name: str, display: str, guide: Guide) -> list[str]:
         lead = ("No network here? Run the command on a computer that has one, with a USB "
                 f"drive's folder after `--dest`. Then copy it into {_folder_words(display, extract_to)}.")
         return [lead, "", *terminal_tabs(tabs, args, steps=False)]
-    lead = ("No network? Put the device's card in your computer. After `--dest`, "
+    # A folder on the card's Linux partition: Windows and macOS show the
+    # small boot partition alone, and no folder there fits --dest.
+    put = ("Put the device's card in your computer." if "windows" in tabs
+           else "Only a Linux computer opens the card.")
+    lead = (f"No network? {put} After `--dest`, "
             f"name the folder the device calls `{extract_to}`.")
     return [lead, "", *terminal_tabs(tabs, args, steps=False),
             f"[More on SD cards](../{CARD_ROUTE_FAQ})", ""]

tests/test_site_entry.py

@@ -937,6 +937,19 @@ class ARouteWithoutANetwork(unittest.TestCase):
         self.assertEqual(_tab_labels(card), set())
         self.assertIn("**Linux**", card)
 
+    def test_a_linux_partition_card_says_why_and_offers_linux_alone(self):
+        """Lakka's /storage is the card's ext4 partition (Lakka-LibreELEC
+        scripts/mkimage): its page offered Windows and macOS tabs for a
+        folder neither can open."""
+        for name in ("lakka", "retropie"):
+            with self.subTest(setup=name):
+                self.assertEqual(siteguides.GUIDES[name].card_run, ("linux",))
+                card = _plain_page(f"platforms/{name}.md").split("No network?", 1)[1]
+                card = card.split("## On the device", 1)[0]
+                self.assertEqual(_tab_labels(card), set())
+                self.assertNotIn("E:\\", card)
+                self.assertIn("Only a Linux computer opens the card.", card)
+
     def test_no_zip_is_promised_for_an_unmarked_setup(self):
         for name in SETUPS:
             if REGISTRY[name].get("release_pack") is True: