fix: only append to appliedNodes after successful node evaluation

[rawadhossain]

Description

This change prevents nodes from appearing in both status.appliedNodes and status.failedNodes during rule reconciliation.

Previously, nodes were added to appliedNodes before evaluateRuleForNode ran. If evaluation fails, the same node ends up in failedNodes as well. so it shows up in both lists in a single reconcile.

There’s also a related case where a node that previously failed but later succeeds can still have a stale entry in failedNodes, so it continues to appear in both lists even after recovery.

To fix this:

• only add nodes to appliedNodes when evaluateRuleForNode succeeds
• remove any existing failedNodes entry for a node when it evaluates successfully
• add tests covering both failure and recovery scenarios

This keeps appliedNodes aligned with its intended meaning (nodes where the taint was successfully managed) and avoids overlap with failedNodes.

Related Issue

Fixes #215

Type of Change

/kind bug

Testing

• Added tests to cover:
  • evaluation failure: node is not added to appliedNodes and appears in failedNodes
  • recovery case: stale failedNodes entry is removed and node is added to appliedNodes
• Ran:
  • make test
  • make lint

Checklist

• make test passes
• make lint passes

[k8s-ci-robot]

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This pull-request has been approved by: rawadhossain
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