feat: match filter input to sidebar search styling

Add search icon, translucent background, and same padding/sizing
as the sidebar's built-in filter input. Placeholder changed to
"Filter..." to match sidebar convention.

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

ui/src/pages/AgentHealth/AgentHealth.module.css

@@ -383,20 +383,27 @@
   margin-bottom: 12px;
 }
 
-/* App name filter */
+/* App name filter — matches sidebar search input styling */
 .appFilterWrap {
   position: relative;
   display: flex;
   align-items: center;
 }
 
+.appFilterIcon {
+  position: absolute;
+  left: 8px;
+  color: var(--text-muted);
+  pointer-events: none;
+}
+
 .appFilterInput {
   width: 180px;
-  height: 28px;
-  padding: 0 24px 0 8px;
-  border: 1px solid var(--border-subtle);
+  height: 29px;
+  padding: 6px 26px 6px 28px;
+  border: 1px solid rgba(255, 255, 255, 0.08);
   border-radius: var(--radius-sm);
-  background: transparent;
+  background: rgba(255, 255, 255, 0.06);
   color: var(--text-primary);
   font-size: 12px;
   font-family: var(--font-body);
@@ -414,7 +421,7 @@
 
 .appFilterClear {
   position: absolute;
-  right: 4px;
+  right: 6px;
   background: transparent;
   border: none;
   color: var(--text-muted);