partition: Improve bidi link down detection

[ieQu1]

No description provided.

[Copilot]

Pull request overview

This PR improves partition/link detection by allowing classy_partition:bidi_link/3 to conclusively return {ok, false} in more “partial data” scenarios (e.g., when one node is missing from classy:info/1), and introduces a new unid_link/3 helper to query one-way connectivity.

Changes:

• Add classy_partition:unid_link/3 and a find_peer_by_nodeid/2 helper to detect one-way link state from a single node’s peer view.
• Enhance classy_partition:bidi_link/3 to return {ok, false} when either direction can be proven disconnected, even if one node is missing from ClusterInfo.
• Update the Common Test suite to validate symmetric bidi/unid detection and the improved “node down” behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
test/classy_SUITE.erl	Renames and expands the link-detection testcase to cover bidi + unid behavior, including node-down cases.
src/classy_partition.erl	Adds unid_link/3, refines bidi_link/3 fallback logic, and introduces peer lookup by node id.

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