style(poc4): simplify HMM visual theme

poc4_active_source_20260714/apps/poc4/mcp_discovery_ui.py

@@ -1134,8 +1134,60 @@ div[data-testid="stMetric"] {
 }
 
 .kb-ops-link:hover {
-  background: #333333;
+  background: #006aab;
-  color: #ffe36b !important;
+  color: #ffffff !important;
+}
+
+/* HMM minimal presentation: one ocean-blue accent, white surfaces, no heavy shading. */
+.stApp,
+section[data-testid="stSidebar"] {
+  background: #f7fafc !important;
+}
+
+.kb-hero,
+.kb-sidebar-card,
+.kb-arch-stage,
+.kb-ops-step,
+.kb-ops-portal,
+div[data-testid="stForm"],
+.st-key-kb_login_container [data-testid="stForm"] {
+  background: #ffffff !important;
+  border-color: #d6e3ec !important;
+  box-shadow: none !important;
+}
+
+.kb-hero::before,
+.kb-section-title.input,
+.kb-panel-title,
+.kb-arch-stage.experience,
+.kb-ops-portal {
+  border-color: #004b87 !important;
+}
+
+.kb-vpd-card,
+div[data-testid="stButton"] > button,
+div[data-testid="stButton"] > button[kind="primary"],
+div[data-testid="stFormSubmitButton"] > button[data-testid="stBaseButton-primaryFormSubmit"],
+.kb-ops-link,
+.st-key-kb_login_container [data-testid="stFormSubmitButton"] button {
+  background: #004b87 !important;
+  border-color: #004b87 !important;
+  color: #ffffff !important;
+  box-shadow: none !important;
+}
+
+div[data-testid="stButton"] > button:hover,
+div[data-testid="stFormSubmitButton"] > button[data-testid="stBaseButton-primaryFormSubmit"]:hover,
+.st-key-kb_login_container [data-testid="stFormSubmitButton"] button:hover,
+.kb-ops-link:hover {
+  background: #006aab !important;
+  color: #ffffff !important;
+}
+
+.kb-vpd-card .kb-vpd-user,
+.kb-vpd-card .kb-vpd-meta,
+.kb-vpd-card .kb-vpd-scope {
+  color: #ffffff !important;
 }
 
 h2, h3 {