feat(npcs): add groups, storyline bindings, and Foundry import

Nested NPC groups with color, graph filter, and scene/storyline binding; Foundry worlds/modules import actors into groups; storyline merge asks on NPC name conflicts and reports NPC counts.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/npcs/NpcsApp.module.css

@@ -158,3 +158,66 @@
   color: var(--text2);
   font-size: 13px;
 }
+
+.groupBlock {
+  display: grid;
+  gap: 4px;
+}
+
+.groupHeader {
+  display: grid;
+  grid-template-columns: auto auto 1fr;
+  align-items: center;
+  gap: 6px;
+  padding: 4px 2px;
+  border-bottom: 1px solid var(--stroke);
+  user-select: none;
+}
+
+.groupToggle {
+  border: 0;
+  background: transparent;
+  color: var(--text2);
+  cursor: pointer;
+  width: 18px;
+  padding: 0;
+  font-size: 11px;
+}
+
+.groupColorDot {
+  width: 10px;
+  height: 10px;
+  border-radius: 999px;
+  flex-shrink: 0;
+}
+
+.groupTitle {
+  font-size: 12px;
+  font-weight: 800;
+  letter-spacing: 0.3px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.groupBody {
+  display: grid;
+  gap: 6px;
+  padding: 4px 0 8px 4px;
+  min-height: 0;
+}
+
+.ungroupedSection {
+  display: grid;
+  gap: 4px;
+  margin-top: 4px;
+}
+
+.ungroupedHeader {
+  font-size: 11px;
+  font-weight: 900;
+  letter-spacing: 0.6px;
+  color: var(--text2);
+  padding: 6px 2px 4px;
+  border-bottom: 1px solid var(--stroke);
+}