fix: tree editor authoring blockers - scroll trap, form density, branching hint

- Replace fixed viewport height with flex layout in NodeEditorPanel
- Make footer sticky so Save/Cancel always reachable
- Compact root node banner to single-line with InfoTip tooltip
- Reduce resolution note from callout box to inline text
- Add answer-first branching hint below options label

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

frontend/src/components/tree-editor/NodeEditorPanel.tsx

@@ -162,7 +162,7 @@ export function NodeEditorPanel({ nodeId, onClose, onSelectType }: NodeEditorPan
   const isRoot = treeStructure?.id === nodeId
 
   return (
-    <div ref={panelRef} className="flex h-[calc(100vh-105px)] w-[400px] shrink-0 flex-col border-l border-border bg-card">
+    <div ref={panelRef} className="flex h-full min-h-0 w-[400px] shrink-0 flex-col border-l border-border bg-card">
       {/* Header */}
       <div className="flex items-center gap-2 border-b border-border px-4 py-3 shrink-0">
         <span className={cn('flex h-5 w-5 shrink-0 items-center justify-center rounded', config.badgeClass)}>
@@ -175,14 +175,14 @@ export function NodeEditorPanel({ nodeId, onClose, onSelectType }: NodeEditorPan
       </div>
 
       {/* Body — scrollable form area */}
-      <div className="min-h-0 flex-1 overflow-y-auto px-4 py-3">
+      <div className="min-h-0 flex-1 overflow-y-auto px-4 py-3 scroll-pb-24">
         {draft.type === 'decision' && <NodeFormDecision node={draft} onUpdate={handleDraftUpdate} />}
         {draft.type === 'action' && <NodeFormAction node={draft} onUpdate={handleDraftUpdate} />}
         {draft.type === 'solution' && <NodeFormResolution node={draft} onUpdate={handleDraftUpdate} />}
       </div>
 
       {/* Footer */}
-      <div className="flex items-center gap-2 border-t border-border px-4 py-3 shrink-0">
+      <div className="sticky bottom-0 flex items-center gap-2 border-t border-border bg-card px-4 py-3 shrink-0">
         <button
           onClick={handleSave}
           disabled={!isDirty}

frontend/src/components/tree-editor/NodeFormDecision.tsx

@@ -82,21 +82,10 @@ export function NodeFormDecision({ node, onUpdate }: NodeFormDecisionProps) {
     <div className="space-y-4">
       {/* Root node banner */}
       {isRootNode && (
-        <div className="rounded-lg border-2 border-blue-500/30 bg-blue-500/10 p-4">
-          <div className="flex items-start gap-3">
-            <div className="rounded-full bg-blue-500/20 p-2">
-              <Play className="h-5 w-5 text-blue-500" />
-            </div>
-            <div>
-              <h3 className="font-semibold text-blue-400">
-                Starting Question
-              </h3>
-              <p className="mt-1 text-sm text-muted-foreground">
-                This is the first question users will see when they start this troubleshooting tree.
-                Each option below creates a different troubleshooting path.
-              </p>
-            </div>
-          </div>
+        <div className="flex items-center gap-2 rounded-lg border border-blue-500/30 bg-blue-500/10 px-3 py-2">
+          <Play className="h-4 w-4 text-blue-500 shrink-0" />
+          <span className="text-sm font-medium text-blue-400">Starting Question</span>
+          <InfoTip text="This is the first question users will see. Each option creates a different troubleshooting path." />
         </div>
       )}
 
@@ -150,6 +139,7 @@ export function NodeFormDecision({ node, onUpdate }: NodeFormDecisionProps) {
             ? "Add as many options as needed (A, B, C, D...). Each option leads to a different troubleshooting path."
             : "Each option can branch to a different next step."} />
         </label>
+        <p className="text-xs text-muted-foreground mt-1">Options become answer placeholders you can fill in later.</p>
         {optionsError && (
           <p className="mt-1 text-xs text-red-400">{optionsError.message}</p>
         )}

frontend/src/components/tree-editor/NodeFormResolution.tsx

@@ -143,10 +143,9 @@ Document what was done and the outcome.
       </div>
 
       {/* Note about terminal node */}
-      <div className="rounded-md bg-emerald-400/10 p-3 text-sm text-emerald-400">
-        <strong>Note:</strong> Solution nodes are terminal - they end the troubleshooting flow.
-        The session will be marked complete when the user reaches this node.
-      </div>
+      <p className="text-xs text-emerald-400/70">
+        Solution nodes are terminal — the session completes when users reach this node.
+      </p>
     </div>
   )
 }