docs(site): rename Overview sidebar labels to fix pagination

Renamed the root 'Overview' entry under 'Functions Reference' to 'Categories'. Also renamed the inner category 'Overview' entries to '{Category} Overview'. Because Starlight uses the sidebar label for the 'Next/Previous' pagination buttons at the bottom of pages, having multiple pages labeled just 'Overview' caused the button text to ambiguously say 'Next: Overview' even when linking to a new category.

docs/build-manual.py

@@ -698,7 +698,7 @@ def build_site(root: Path, out: Path) -> list[dict]:
             functions_group = {
                 "label": fm["title"],
                 "collapsed": True,
-                "items": [{"label": "Overview", "link": f"/{slug_dir}/"}],
+                "items": [{"label": "Categories", "link": f"/{slug_dir}/"}],
             }
             sidebar.append(functions_group)
             continue
@@ -756,7 +756,7 @@ def build_site(root: Path, out: Path) -> list[dict]:
                 "label": fm["title"],
                 "collapsed": True,
                 "items": [
-                    {"label": "Overview", "link": f"/{slug_dir}/{category}/"},
+                    {"label": f"{fm['title']} Overview", "link": f"/{slug_dir}/{category}/"},
                     *links,
                 ],
             }

docs/verify-manual.py

@@ -760,7 +760,7 @@ def test_sidebar_has_no_duplicate_functions_entry():
     assert group["label"] not in labels[1:], (
         f"'{group['label']}' is repeated inside its own group: {labels}"
     )
-    assert labels[0] == "Overview", f"group should lead with Overview, got {labels[0]}"
+    assert labels[0] == "Categories", f"group should lead with Categories, got {labels[0]}"
     assert not any(
         "autogenerate" in item for item in group["items"]
     ), "categories should be listed explicitly, not autogenerated from slugs"