fix: sidebar spacing adjustments

- Remove margin-bottom from topLinks
- Nav group header: zero top/bottom padding, 12px margin-bottom
- Remove h3 margin inside sidebar nav groups

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rsbh

packages/chronicle/src/themes/default/Layout.module.css

@@ -76,7 +76,6 @@
 
 .topLinks {
   width: 100%;
-  margin-bottom: var(--rs-space-7);
   display: flex;
   flex-direction: column;
   gap: 0;
@@ -193,6 +192,9 @@
 
 .navGroup .navGroupHeader {
   margin: 0;
+  margin-bottom: var(--rs-space-4);
+  padding-top: 0;
+  padding-bottom: 0;
 }
 
 .navGroup[data-depth='1'] .navGroupHeader {
@@ -226,6 +228,10 @@
   letter-spacing: var(--rs-letter-spacing-small);
 }
 
+.sidebar :global([class*="nav-group"]) h3 {
+  margin: 0;
+}
+
 .navGroupChevron {
   margin-left: auto;
 }