[FA-28] Improve explanation of board representation to agent

[scott-clare1]

This PR adds a more detailed explanation of the board to the agent and includes a field for whether the agent is in check or not.

Tom was finding that the agent was getting confused about the layout of the board, the accompanying explanation hopes to reduce this.

Checklist

Please ensure you have done the following:

• I have read the CONTRIBUTING guide.
• I have updated the documentation if required.
• I have added tests which cover my changes.

Type of change

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• Bug Fix (non-breaking change, fixing an issue)
• New feature (non-breaking change to add functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (add details above)

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