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Many chat clients allow you to press the up/down arrow to recall what you've previously typed. This may be useful functionality for our webchat client.

Implementing this will require keeping a FIFO buffer of previous input entries, storing only a certain number of entries so that long-term webchat use doesn't continue to grow memory use. The limit may be dozens of messages, just not unlimited. Starting with a down arrow should recall the oldest message in the buffer.

When done, attach your changed commands.js to this task.