Add grouped relationship display in note list for entity views

When a Project/Responsibility/Procedure/Experiment is selected in the sidebar,
the note list now groups related items by relationship type (Children, Events,
Referenced By, Belongs To, Related To) instead of showing a flat list. The entity
title is shown in the header, type filter pills are hidden, and search works
within groups.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/NoteList.css

@@ -26,6 +26,11 @@
   margin: 0;
   font-size: 14px;
   font-weight: 600;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  min-width: 0;
+  flex: 1;
 }
 
 .note-list__header-right {
@@ -270,3 +275,31 @@
   border-left: 3px solid #4caf50;
   padding-left: 13px;
 }
+
+/* Relationship groups */
+.note-list__group {
+  border-top: 1px solid rgba(42, 42, 74, 0.5);
+}
+
+.note-list__group-header {
+  padding: 10px 16px 4px;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+}
+
+.note-list__group-label {
+  font-size: 11px;
+  font-weight: 600;
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
+  color: #666;
+}
+
+.note-list__group-count {
+  font-size: 10px;
+  color: #555;
+  background: #2a2a4a;
+  padding: 1px 6px;
+  border-radius: 8px;
+}