fix(component): honor image pull policy for kbagent

[weicao]

Summary

• make component kbagent and init-kbagent honor KUBEBLOCKS_IMAGE_PULL_POLICY
• keep the previous default by falling back to IfNotPresent when the config is empty
• add focused unit coverage for the main kbagent container and the init-kbagent path

Scope

This only changes the component controller kbagent injection path. Existing DataProtection, custom Ops, and other job paths that already read KBImagePullPolicy are unchanged.

The empty-config fallback to IfNotPresent is deliberate backward compatibility with the previous hardcoded component kbagent behavior. It differs from some job paths that leave an empty pull policy for Kubernetes defaults, but avoids changing component kbagent behavior when KUBEBLOCKS_IMAGE_PULL_POLICY is not set.

Validation

• go test ./pkg/controller/component -run TestBuildKBAgentContainerUsesConfiguredImagePullPolicy -count=1
• go test -c ./pkg/controller/component
• git diff --check

Local Ginkgo/envtest execution is not counted as passed because this machine is missing /usr/local/kubebuilder/bin/etcd; CI should provide that coverage.

Context

MariaDB T6 validation hit a repeated kbagent tools image tag-alias trap while the KubeBlocks deployment had KUBEBLOCKS_IMAGE_PULL_POLICY=Never. The controller component path still injected kbagent with hardcoded IfNotPresent, so pod image resolution could re-enter the registry path.

[apecloud-bot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.49%. Comparing base (a375e10) to head (6c7af05).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10253      +/-   ##
==========================================
+ Coverage   52.42%   52.49%   +0.06%     
==========================================
  Files         533      533              
  Lines       61230    61237       +7     
==========================================
+ Hits        32099    32144      +45     
+ Misses      25872    25837      -35     
+ Partials     3259     3256       -3     

Flag	Coverage Δ
unittests	52.49% <100.00%> (+0.06%)	⬆️

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