Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

scripts/check_docs_links.py

@@ -4,25 +4,30 @@ Checks only local file links (relative paths) and reports missing targets.
 
 Run from the repository root using the project's Python environment.
 """
+
 import re
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
-DOCS = ROOT / 'docs'
+DOCS = ROOT / "docs"
 
 MD_LINK_RE = re.compile(r"\[([^\]]+)\]\(([^)]+)\)")
 
 errors = []
 
-for md in DOCS.rglob('*.md'):
-    text = md.read_text(encoding='utf-8')
+for md in DOCS.rglob("*.md"):
+    text = md.read_text(encoding="utf-8")
     for m in MD_LINK_RE.finditer(text):
         label, target = m.groups()
         # skip URLs
-        if target.startswith('http://') or target.startswith('https://') or target.startswith('#'):
+        if (
+            target.startswith("http://")
+            or target.startswith("https://")
+            or target.startswith("#")
+        ):
             continue
         # strip anchors
-        target_path = target.split('#')[0]
+        target_path = target.split("#")[0]
         # if link is to a directory index, allow
         candidate = (md.parent / target_path).resolve()
         if candidate.exists():
@@ -30,14 +35,16 @@ for md in DOCS.rglob('*.md'):
         # check common implicit index: target/ -> target/README.md or target/index.md
         candidate_dir = md.parent / target_path
         if candidate_dir.is_dir():
-            if (candidate_dir / 'README.md').exists() or (candidate_dir / 'index.md').exists():
+            if (candidate_dir / "README.md").exists() or (
+                candidate_dir / "index.md"
+            ).exists():
                 continue
         errors.append((str(md.relative_to(ROOT)), target, label))
 
 if errors:
-    print('Broken local links found:')
+    print("Broken local links found:")
     for src, tgt, label in errors:
-        print(f'- {src} -> {tgt}  ({label})')
+        print(f"- {src} -> {tgt}  ({label})")
     exit(2)
 
-print('No broken local links detected.')
+print("No broken local links detected.")