is_stable is true for nodes with lagging block heights

[ppca]

If a node starts at a very early block height and has been syncing but is still way behind, is_stable will still show true

[ppca]

Nodes could publish their current block height in their state, i.e. {url}/state, and nodes can query each other for block heights, and they'd know whether each other are behind or not

[ppca]

Could query it from RPC endpoint too, and parse it from the json response. Then the node does not need to query other nodes, it knows how delayed it is and can publish is_stable based on comparison of its height v.s. rpc endpoint