Add TreeNode validation to prevent detached nodes causing inconsistent tool results

[Copilot]

Detached TreeNodes (nodes without parent chain) cause contradictory tool call results: get_topic() returns child count from metadata while list_children() returns empty from missing edgeCollection.

Changes

TreeNode Validation

• Added isValidTreeNode() to verify node structure before use
• Validates parent chain exists for non-root nodes (proves tree connectivity)
• Verifies edgeCollection presence for child enumeration
• Rejects detached nodes with console warnings

Integration

• Validates currentNode in sendMessage() before passing to tool execution
• Falls back to undefined if node is detached or invalid
• Prevents tools from receiving inconsistent tree state

Implementation

private isValidTreeNode(node?: TopicNode): boolean {
  if (!node || typeof node.path !== 'function') return false
  
  const path = node.path()
  // Non-root nodes must have parent to prove tree connectivity
  if (path && path.length > 0 && !node.parent) {
    console.warn('Detached TreeNode detected:', path)
    return false
  }
  
  if (!node.edgeCollection) {
    console.warn('TreeNode missing edgeCollection:', path)
    return false
  }
  
  return true
}

Detached nodes now rejected early with diagnostic logging, eliminating metadata vs structure inconsistencies.

Original prompt

Ensure the live LLM tests run successfully

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.