fix: align english homepage author grid

Top-align the English homepage author cards, enlarge the row gap, and normalize avatar sizing so author portraits line up consistently.

en_chapters/frontpage.html

@@ -41,6 +41,10 @@ h2.toc {
 }
 .author-item {
   max-width: 300px;
+  width: 100%;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
 }
 .author-item h3 {
     padding-top: 25px;
@@ -49,6 +53,17 @@ h2.toc {
 .author-item img {
     border-radius: 50%;
     width: 120px;
+    height: 120px;
+    object-fit: cover;
+}
+.authors.mdl-grid {
+    align-items: flex-start;
+    row-gap: calc(24px + 1.5em);
+}
+.authors .mdl-cell {
+    display: flex;
+    align-items: flex-start;
+    justify-content: center;
 }
 .authors h4 {
     width: 100%;

tests/test_prepare_mdbook.py

@@ -7,6 +7,9 @@ from pathlib import Path
 from tools.prepare_mdbook import build_title_cache, rewrite_markdown, write_summary
 
 
+REPO_ROOT = Path(__file__).resolve().parents[1]
+
+
 class PrepareMdBookTests(unittest.TestCase):
     def test_write_summary_skips_placeholder_pages(self) -> None:
         with tempfile.TemporaryDirectory() as tmpdir:
@@ -199,6 +202,15 @@ Reference :cite:`smith2024`.
 
             self.assertNotIn('openmlsys-frontpage-switch', rewritten)
 
+    def test_english_frontpage_author_grid_uses_top_aligned_spacing(self) -> None:
+        frontpage = (REPO_ROOT / "en_chapters" / "frontpage.html").read_text(encoding="utf-8")
+
+        self.assertIn(".authors.mdl-grid {", frontpage)
+        self.assertIn("align-items: flex-start;", frontpage)
+        self.assertIn("row-gap: calc(24px + 1.5em);", frontpage)
+        self.assertIn("height: 120px;", frontpage)
+        self.assertIn("object-fit: cover;", frontpage)
+
 
 if __name__ == "__main__":
     unittest.main()