feat(ssh): skip pubkey auth if PubkeyAuthentication "no" in config

[kke]

wires the SSH config PubkeyAuthentication key to ssh connection initialization

API breaking is not an issue as rig v2 hasn't been released yet.

[Copilot]

Pull request overview

This PR wires the PubkeyAuthentication SSH config option into rig’s SSH client configuration so that public-key based authentication can be skipped when the config explicitly disables it.

Changes:

• Add Connection.loadAgentSigners helper to encapsulate ssh-agent signer discovery and logging.
• Honor ssh_config PubkeyAuthentication no by skipping ssh-agent and IdentityFile-based key authentication.
• Add a unit test asserting clientConfig returns a non-retryable error when pubkey auth is disabled and no other auth methods are available.

Reviewed changes

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

File	Description
protocol/ssh/connection.go	Skip agent/identity-file public key auth when PubkeyAuthentication is disabled; refactor agent signer loading into a helper.
protocol/ssh/connection_test.go	Add coverage for the “PubkeyAuthentication no” behavior returning a non-retryable error when no other auth is configured.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

protocol/ssh/connection.go:409

• On homedir.Expand error, keyPath is overwritten with the (empty) return value, so the trace log can lose the original path that failed to expand. Keep the original value for logging to make diagnostics accurate.

		keyPath, err := homedir.Expand(keyPath)
		if err != nil {
			log.Trace(ctx, "expand keypath", log.FileAttr(keyPath), log.ErrorAttr(err))
			continue
		}

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.