Prevent self-reference in Node hierarchy with ArgumentException

[Copilot]

Adding a node to itself as a child currently causes StackOverflowException during UpdateModelMatrix() recursion, making debugging difficult.

Changes

• Self-reference validation: Added check in ContainableNode.Add() and Insert() to throw ArgumentException with clear message when node == this
• Bug fix: Corrected Insert() method's parent removal logic from Remove(this) to Remove(node) - was attempting to remove wrong node from parent

Example

var container = new Container();
container.Add(container);  // Now throws: ArgumentException: "ノードの子要素に自分自身を追加することはできません。"
                          // Previously: StackOverflowException (unclear cause)

Tests added to verify exception behavior and correct parent reassignment.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: node /home/REDACTED/work/Promete/Promete/Promete.Docs/node_modules/.bin/astro build (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Nodeの子要素として自分自身を追加しようとしたら例外を出すようにする</issue_title>
<issue_description>現時点で、Nodeの子要素に自分を追加するとStackOverFlowExceptionがスローされる

不具合の原因がわかりづらいので、事前にArgumentException例外を出すようにする</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Nodeの子要素として自分自身を追加しようとしたら例外を出すようにする #51

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