Research: Metric for quote age/"staleness" in order book

[skynetcap]

Research how we can rank or quantify the age of a quote in the order book.

Some possibilities:

• Diff-ing the order book and recording timestamps.
• Investigate on-chain Slab data structure for a deterministic approach
• Correlate to TXID (somehow)

This metric would then be displayed to the user, quantitatively (data column), visually (color), or both, or something else creative.