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,
                 ],
             }