Gateway node selection strategy fix - hash topic identifier instead of full bytes for stable routing

[api-Hypernova]

The stable hashing algorithm was including the topic's 1-byte kind prefix, causing different message types for the same entity (e.g., key_packages and welcome_messages for the same installation) to route to different nodes.

This fix ensures that only the identifier portion of the topic is hashed, so all message types for the same entity route to the same node.

[macroscopeapp]

Hash topic identifier in selectors.HashKey to stabilize gateway routing and update tests to use a ±10% tolerance and new node selection order in stable.go and node_selector_test.go

Change selectors.HashKey to hash topic.Identifier() instead of topic.Bytes(), and update tests for distribution tolerance to ±10% and the expected banned-node reselection order.

📍Where to Start

Start with selectors.HashKey in stable.go, then review test updates in node_selector_test.go.

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Macroscope summarized d787ad5.

[macroscopeapp]

Hash topic identifier in selectors.HashKey to stabilize gateway routing and update tests to use a ±10% tolerance and new node selection order in stable.go and node_selector_test.go

Change selectors.HashKey to hash topic.Identifier() instead of topic.Bytes(), and update tests for distribution tolerance to ±10% and the expected banned-node reselection order.

📍Where to Start

Start with selectors.HashKey in stable.go, then review test updates in node_selector_test.go.

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Macroscope summarized d787ad5.