fix: agent node deletion, inspector layout, and header overlap

- Enable Delete-key removal of agent nodes on the canvas; system nodes
  remain non-deletable. Removals route through the authoritative
  removeAgent path which prevents deleting the last agent.
- Stack Model and Reasoning selects vertically in the inspector panel
  so they fit within the 320px-wide column without truncation.
- Add right padding (pr-36 / 144px) to the editor header so the Save
  and Delete buttons clear the Windows title-bar overlay controls.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/components/PatternEditor.tsx

@@ -231,7 +231,7 @@ export function PatternEditor({
   return (
     <div className="flex h-full flex-col">
       {/* Header */}
-      <div className="drag-region flex items-center justify-between border-b border-[var(--color-border)] px-5 pb-3 pt-3">
+      <div className="drag-region flex items-center justify-between border-b border-[var(--color-border)] pb-3 pl-5 pr-36 pt-3">
         <div className="flex items-center gap-3">
           <button
             className="no-drag flex size-8 items-center justify-center rounded-lg text-zinc-400 transition hover:bg-zinc-800 hover:text-zinc-200"
@@ -320,6 +320,7 @@ export function PatternEditor({
               pattern={pattern}
               availableModels={availableModels}
               onGraphChange={emitGraphChange}
+              onAgentRemove={removeAgent}
               onNodeSelect={setSelectedNodeId}
               selectedNodeId={selectedNodeId}
             />

src/renderer/components/pattern-graph/PatternGraphCanvas.tsx

@@ -39,6 +39,7 @@ interface PatternGraphCanvasProps {
   pattern: PatternDefinition;
   availableModels?: ReadonlyArray<ModelDefinition>;
   onGraphChange: (graph: PatternGraph) => void;
+  onAgentRemove: (agentId: string) => void;
   onNodeSelect: (nodeId: string | null) => void;
   selectedNodeId: string | null;
 }
@@ -47,6 +48,7 @@ function PatternGraphCanvasInner({
   pattern,
   availableModels,
   onGraphChange,
+  onAgentRemove,
   onNodeSelect,
   selectedNodeId,
 }: PatternGraphCanvasProps) {
@@ -69,12 +71,28 @@ function PatternGraphCanvasInner({
 
   const handleNodesChange: OnNodesChange<Node<GraphNodeData>> = useCallback(
     (changes) => {
-      onNodesChange(changes);
+      // Intercept node removals and route agent deletions through the
+      // authoritative removal path (which also removes from pattern.agents).
+      const removals = changes.filter((c) => c.type === 'remove');
+      const nonRemovals = changes.filter((c) => c.type !== 'remove');
 
-      const hasDragStart = changes.some(
+      for (const removal of removals) {
+        if (removal.type === 'remove') {
+          const graphNode = graph.nodes.find((n) => n.id === removal.id);
+          if (graphNode?.kind === 'agent' && graphNode.agentId) {
+            onAgentRemove(graphNode.agentId);
+          }
+        }
+      }
+
+      if (nonRemovals.length > 0) {
+        onNodesChange(nonRemovals);
+      }
+
+      const hasDragStart = nonRemovals.some(
         (c) => c.type === 'position' && 'dragging' in c && c.dragging,
       );
-      const hasDragStop = changes.some(
+      const hasDragStop = nonRemovals.some(
         (c) => c.type === 'position' && !('dragging' in c && c.dragging),
       );
 
@@ -91,7 +109,7 @@ function PatternGraphCanvasInner({
         });
       }
     },
-    [onNodesChange, pattern, onGraphChange, setNodes],
+    [onNodesChange, pattern, graph, onGraphChange, onAgentRemove, setNodes],
   );
 
   const handleEdgesChange: OnEdgesChange = useCallback(

src/renderer/components/pattern-graph/PatternGraphInspector.tsx

@@ -184,7 +184,7 @@ function AgentNodeInspector({
         value={agent.name}
       />
 
-      <div className="grid gap-3 sm:grid-cols-2">
+      <div className="space-y-3">
         <ModelSelect
           models={availableModels}
           onChange={(value) => {

src/renderer/lib/patternGraph.ts

@@ -96,7 +96,7 @@ export function toCanvasNodes(
       },
       draggable: true,
       selectable: true,
-      deletable: false,
+      deletable: node.kind === 'agent',
     };
   });
 }