feat: reference pages answer every hash and field

A platform or emulator record whose value designates a collection
file carries its sha1 and is filed under the file's other hashes, so
a SHA1 paste finds the setups listing it by MD5. The data page shows
every manifest field, writes URL templates as code, states the EmuDeck
rule, the browser lookup and the empty lists. systems.json gives every
id holding files a page, Files to source splits at 100 rows with an
upload link per file, and MiSTer and BizHawk get no empty core table.

tests/test_site_r3_reference.py

@@ -296,7 +296,7 @@ class ManifestsArePublished(unittest.TestCase):
             self.assertIn(f"| `{field}` | {generate_site._escape_tags(description)} |", page)
         self.assertIn("## Platform manifests", page)
         self.assertIn("**Licence:**", page)
-        self.assertIn("## Hosting and limits", page)
+        self.assertIn("## Hosting, rate limits and caching", page)
         # The endpoints first, the DAT below them.
         self.assertLess(page.index("## Stable JSON endpoints"), page.index("The DAT is Logiqx XML"))
 
@@ -449,7 +449,7 @@ class SourceLinksGoWhereTheFileIs(unittest.TestCase):
     def tearDown(self):
         sitesources._tree_paths.cache_clear()
 
-    def _render(self, tree: frozenset[str] | None) -> str:
+    def _render(self, tree: frozenset[str]) -> str:
         original = sitesources._tree_paths
         sitesources._tree_paths = lambda repo, pin: tree  # type: ignore[assignment]
         try:
@@ -464,9 +464,12 @@ class SourceLinksGoWhereTheFileIs(unittest.TestCase):
         self.assertIn("`src/core/loader/ncch.cpp:151-164`", text)
         self.assertNotIn("3dsTrident/blob/" + "b" * 40 + "/src/core/loader", text)
 
-    def test_without_a_cached_tree_the_declarations_decide(self):
-        text = self._render(None)
-        self.assertIn("3dsTrident/blob/" + "b" * 40 + "/src/core/loader/ncch.cpp", text)
+    def test_a_path_no_tree_confirmed_is_not_linked(self):
+        """Round 4: without a tree the declared repository took the path,
+        and the deploy, which has no tree cache, linked 30 paths to a 404."""
+        text = self._render(frozenset())
+        self.assertNotIn("](https://", text)
+        self.assertIn("`src/core/loader/ncch.cpp:151-164`", text)
 
     def test_every_rendered_link_is_in_its_cached_tree(self):
         """Offline: each link the pages render points at a path the cached