site: take the six doors off the landing page

The page is now three things: what bench is, what installing costs, and
why to bother. The header nav is the way into the docs.

Removing them takes their CSS with them (.doors/.door* in the base sheet
and in all three breakpoints) and two tests that existed only for them —
the six-are-distinct check here and TheDoorsOpenOntoArticles in
test_site_pages. The hero-buttons test survives its class, renamed to say
what it now guards: the landing page's only links into the docs.

One test needed retargeting rather than deleting.
test_it_fails_before_anything_is_written removed /concepts/team-mode/
from the manifest to prove a dead internal link stops the build before
anything is written — but the link it relied on was a door. It now aims
at /guides/install/, which the hero button still hard-links.

Side effect worth having: the two reasons in "Why bench?" that nearly
repeated doors 03 and 04 no longer sit above them.

tests/test_site_landing.py

@@ -11,8 +11,8 @@ Three promises, each mechanised below:
   held against the source that prints it — install.py's setup questions,
   board.py's startup. A reworded prompt fails here rather than quietly
   turning the strongest thing on the page into fiction.
-- **Every door opens.** The six cards point at routes this build writes,
-  and a link that resolves to nothing fails the build instead of shipping.
+- **Its links go somewhere.** A link that resolves to nothing fails the
+  build instead of shipping.
 
     python3 -m unittest discover -s tests
 """
@@ -135,24 +135,9 @@ class TheTerminalIsATranscript(LandingCase):
         self.assertIn("abridged", self.home)
 
 
-class TheDoorsOpen(LandingCase):
-    """Six doors, each a page this site builds."""
-
-    def doors(self) -> list:
-        return re.findall(r'<a class="door[^"]*" href="([^"]+)"', self.home)
-
-    def test_there_are_six_and_they_are_distinct(self):
-        self.assertEqual(6, len(self.doors()))
-        self.assertEqual(6, len(set(self.doors())))
-
-    def test_each_one_is_a_route_the_build_writes(self):
-        routes = {page["path"] for page in self.manifest["pages"]}
-        for door in self.doors():
-            with self.subTest(door=door):
-                self.assertIn(door, routes)
-                self.assertTrue(
-                    BUILDER.target_for(self.out, door).is_file(),
-                    f"{door} is in the manifest but produced no page")
+class TheHeroLeadsSomewhere(LandingCase):
+    """The landing page's only links into the docs, now that the six
+    doors are gone: these two buttons and the header nav."""
 
     def test_both_hero_buttons_go_somewhere_real(self):
         """One to the install guide, one to the repository."""
@@ -286,10 +271,12 @@ class ADeadInternalLinkStopsTheBuild(ScratchCase):
         self.assertIn("does not write", result.stderr)
 
     def test_it_fails_before_anything_is_written(self):
-        """As drift does: the last good build stays up."""
+        """As drift does: the last good build stays up. Aimed at the
+        install guide because the hero button hard-links it — the
+        landing page's other internal links went with the doors."""
         manifest = self.repo.manifest()
         manifest["pages"] = [page for page in manifest["pages"]
-                             if page["path"] != "/concepts/team-mode/"]
+                             if page["path"] != "/guides/install/"]
         self.repo.write_manifest(manifest)
         self.repo.build()
         self.assertFalse(self.repo.out.exists(),

tests/test_site_pages.py

@@ -32,7 +32,6 @@ HEADING_ID = re.compile(r'<h2 id="([^"]+)"')
 TOC_LINK = re.compile(r'class="toc-link" href="#([^"]+)"')
 SIDE_HERE = re.compile(r'class="side-link side-here" href="([^"]+)"')
 GUTTER_LINK = re.compile(r'class="gutter-link" href="([^"]+)"')
-DOOR = re.compile(r'class="door[^"]*" href="([^"]+)"')
 LEDE = re.compile(r'<p class="prose-lede">(.*?)</p>', re.S)
 # Both rails are written twice — the column the design draws, and the
 # folded <details> strip that replaces it below the breakpoint. So these
@@ -269,19 +268,6 @@ class EditThisPageOpensTheSection(BuiltSite):
                 'class="gutter-link" href="')[-1].split('"')[0])
 
 
-class TheDoorsOpenOntoArticles(BuiltSite):
-    """Task 33 put six doors on the landing page. This is the other end of
-    them."""
-
-    def test_every_door_lands_on_a_page_in_the_flow(self):
-        routes = {entry["path"] for entry in self.flow}
-        doors = DOOR.findall(self.page("/"))
-        self.assertEqual(6, len(doors))
-        for door in doors:
-            self.assertIn(door, routes,
-                          f"the door to {door} opens onto nothing")
-
-
 @needs_renderer
 class MarkdownComesOutAsMarkup(BuiltSite):
     """The edge case: a table, a fenced code block and a nested list have