style: enforce 12px minimum font size across all components

Add --font-size-min: 12px token to tokens.css. Replace all 10px and 11px
font-size declarations with 12px across 54 CSS module files for improved
readability.

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

src/design-system/layout/Sidebar/Sidebar.module.css

@@ -70,7 +70,7 @@
 
 .version {
   font-family: var(--font-mono);
-  font-size: 10px;
+  font-size: 12px;
   color: var(--sidebar-muted);
   margin-left: 4px;
 }
@@ -238,7 +238,7 @@
 }
 
 .treeSectionLabel {
-  font-size: 10px;
+  font-size: 12px;
   font-weight: 600;
   text-transform: uppercase;
   letter-spacing: 1px;
@@ -313,7 +313,7 @@
   padding: 0;
   margin: 0;
   color: var(--sidebar-muted);
-  font-size: 11px;
+  font-size: 12px;
   cursor: pointer;
   line-height: 1;
   display: flex;
@@ -345,7 +345,7 @@
 /* Badge */
 .treeBadge {
   font-family: var(--font-mono);
-  font-size: 10px;
+  font-size: 12px;
   color: var(--sidebar-muted);
   background: rgba(255, 255, 255, 0.06);
   padding: 1px 6px;