style(poc4): remove legacy hero decoration

poc4_active_source_20260714/apps/poc4/mcp_discovery_ui.py

@@ -316,27 +316,17 @@ section[data-testid="stSidebar"] input:disabled {
 }
 
 .kb-hero {
-  position: relative;
-  overflow: hidden;
   display: grid;
   grid-template-columns: minmax(0, 1fr) 236px;
   grid-template-areas: "main logo";
   gap: 24px;
   align-items: start;
   border: 1px solid var(--kb-line);
-  border-radius: 20px;
+  border-radius: 8px;
   padding: 28px;
   margin-bottom: 24px;
   background: #ffffff;
-  box-shadow: 0 14px 32px rgba(17, 17, 17, 0.08);
-}
-
-.kb-hero::before {
-  content: "";
-  position: absolute;
-  inset: 0 auto 0 0;
-  width: 8px;
-  background: var(--kb-yellow);
+  box-shadow: none;
 }
 
 .kb-hero-main {
@@ -1156,7 +1146,6 @@ div[data-testid="stForm"],
   box-shadow: none !important;
 }
 
-.kb-hero::before,
 .kb-section-title.input,
 .kb-panel-title,
 .kb-arch-stage.experience,