fix: copilot node context — use title/question/description over legacy content field

_build_flow_context() was reading node.get('content') which was only
present on old KB-imported steps. Now falls back through title →
question → description → content → label so all node types (decision,
action, solution, procedural step) show correctly in the copilot context.

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

backend/app/services/copilot_service.py

@@ -51,7 +51,15 @@ def _build_flow_context(tree: Tree, current_node_id: Optional[str]) -> str:
         node = _find_node(tree.tree_structure, current_node_id)
         if node:
             parts.append(f"Current node type: {node.get('type', 'unknown')}")
-            parts.append(f"Current node: {node.get('content', node.get('label', 'Unknown'))}")
+            node_label = (
+                node.get('title')
+                or node.get('question')
+                or node.get('description')
+                or node.get('content')
+                or node.get('label')
+                or 'Unknown'
+            )
+            parts.append(f"Current node: {node_label}")
             # Add options if it's a question/decision node
             children = node.get("children", [])
             if children and isinstance(children, list):