feat(website): generate static pages for subcategories

Co-Authored-By: Claude <noreply@anthropic.com>

website/build.py

@@ -381,6 +381,40 @@ def build(repo_root: Path) -> None:
             encoding="utf-8",
         )
 
+    seen_subcats: set[tuple[str, str]] = set()
+    for category in categories:
+        for entry in entries:
+            for sub in entry.get("subcategories", []):
+                if sub["value"].split(" > ", 1)[0] != category["name"]:
+                    continue
+                key = (category["slug"], sub["slug"])
+                if key in seen_subcats:
+                    continue
+                seen_subcats.add(key)
+                sub_entries = [
+                    e for e in entries
+                    if any(s["value"] == sub["value"] for s in e.get("subcategories", []))
+                ]
+                page_dir = categories_dir / category["slug"] / sub["slug"]
+                page_dir.mkdir(parents=True, exist_ok=True)
+                synthetic = {
+                    "name": sub["name"],
+                    "slug": sub["slug"],
+                    "description": "",
+                    "description_html": "",
+                }
+                (page_dir / "index.html").write_text(
+                    tpl_category.render(
+                        category=synthetic,
+                        category_url=subcategory_public_url(category["slug"], sub["slug"]),
+                        entries=sub_entries,
+                        total_categories=len(categories),
+                        page_kind="subcategory",
+                        parent_category=category,
+                    ),
+                    encoding="utf-8",
+                )
+
     static_src = website / "static"
     static_dst = site_dir / "static"
     if static_src.exists():

website/tests/test_build.py

@@ -542,6 +542,41 @@ class TestBuild:
         assert 'id="hero-category-heading">Browse by category</h2>' in html
         assert 'class="hero-category-link" href="/categories/ai-and-agents/"' in html
 
+    def test_build_creates_subcategory_pages(self, tmp_path):
+        readme = textwrap.dedent("""\
+            # T
+
+            ---
+
+            **Web**
+
+            ## Web Frameworks
+
+            - Synchronous
+
+                - [django](https://example.com/django) - Sync framework.
+
+            - Asynchronous
+
+                - [fastapi](https://example.com/fastapi) - Async framework.
+
+            # Contributing
+
+            Done.
+        """)
+        self._copy_real_templates(tmp_path)
+        (tmp_path / "README.md").write_text(readme, encoding="utf-8")
+        build(tmp_path)
+
+        site = tmp_path / "website" / "output"
+        sync = (site / "categories" / "web-frameworks" / "synchronous" / "index.html").read_text(encoding="utf-8")
+        async_ = (site / "categories" / "web-frameworks" / "asynchronous" / "index.html").read_text(encoding="utf-8")
+
+        assert "django" in sync
+        assert "fastapi" not in sync
+        assert "fastapi" in async_
+        assert "django" not in async_
+
     def test_build_creates_group_pages(self, tmp_path):
         readme = textwrap.dedent("""\
             # T