feat(ui): world map — jump by clicking chart fields (#19)

Remove the bottom JUMP ROUTES button list; systems adjacent to the current
one become clickable galactic-chart nodes (same POST /api/jump flow, same
state refreshes). Current + unreachable systems are dimmed and not
clickable. NodeGraph gains optional onNodeClick + per-node disabled
(backward-compatible); two smoke tests updated to click chart fields.

components/ui/node-graph.tsx

@@ -13,6 +13,7 @@ export interface NodeGraphNode {
   y: number
   status?: NodeStatus
   sublabel?: string
+  disabled?: boolean   // not clickable even when onNodeClick is set (e.g. the current system)
 }
 
 export interface NodeGraphEdge {
@@ -29,6 +30,7 @@ export interface NodeGraphProps extends React.HTMLAttributes<HTMLDivElement> {
   title?: string
   height?: number
   directed?: boolean
+  onNodeClick?: (id: string) => void   // makes non-disabled nodes clickable buttons
 }
 
 const VARIANT_COLORS: Record<NodeGraphVariant, string> = {
@@ -59,6 +61,7 @@ const NodeGraph = React.forwardRef<HTMLDivElement, NodeGraphProps>(
       title,
       height   = 320,
       directed = false,
+      onNodeClick,
       style,
       ...props
     },
@@ -219,13 +222,21 @@ const NodeGraph = React.forwardRef<HTMLDivElement, NodeGraphProps>(
               const cy = nodePy(node)
               const isHovered   = hovered === node.id
               const statusColor = node.status ? STATUS_COLOR[node.status] : color
+              const clickable   = !!onNodeClick && !node.disabled
 
               return (
                 <g
                   key={node.id}
                   onMouseEnter={() => setHovered(node.id)}
                   onMouseLeave={() => setHovered(null)}
-                  style={{ cursor: 'default' }}
+                  onClick={clickable ? () => onNodeClick(node.id) : undefined}
+                  onKeyDown={clickable
+                    ? (e) => { if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); onNodeClick(node.id) } }
+                    : undefined}
+                  role={clickable ? 'button' : undefined}
+                  tabIndex={clickable ? 0 : undefined}
+                  aria-label={clickable ? node.label.toUpperCase() : undefined}
+                  style={{ cursor: clickable ? 'pointer' : 'default' }}
                 >
                   {/* Background */}
                   <rect