[Bugfix] fix spec/label/annotation changes can't trigger redownload

[pallasathena92]

What this PR does

Replaces shouldDownloadModelInUpdateEvent (which used defaultDecision=false) with shouldDownloadModel (which uses defaultDecision=true). When a model has spec/label/annotation changes AND has no NodeSelector or NodeAffinity, it will now trigger generateDownloadOverrideTask.

Why we need it

What shouldDownloadModelCommon does:

1. storageSpec == nil → return true
2. PVC storage → return false
3. NodeSelector doesn't match this node → return false
4. NodeAffinity doesn't match this node → return false
5. Nothing rejected it → return defaultDecision
   The key difference:

shouldDownloadModel passes defaultDecision = true → "yes, download unless something explicitly rejects it"
shouldDownloadModelInUpdateEvent passes defaultDecision = false → "no, don't download unless... nothing can make it true"

With this function, we can't trigger model redownload whtn the model has spec/label/annotation changes.

What changes:

• add policyChanged check in updateClusterBaseModel and updateBaseModel to check if downloadPolicy update need to trigger downloadOverrideTask
  • current isToDownloadOverrideDueToDownloadPolicyBasedOnBM is scoped to HuggingFace only. will refactor this when we support download policy in all storageType.
• add ignoreDownloadPolicy when spec/label/annotation changes check.
• combine these two checks before downloadOverrideTask generation to avoid redundant task generation.

How to test

Checklist

• Tests added/updated (if applicable)
• Docs updated (if applicable)
• make test passes locally

[gemini-code-assist]

Code Review

This pull request simplifies the model download logic by replacing shouldDownloadModelInUpdateEvent with shouldDownloadModel and removing the deprecated function. The review feedback identifies that this change introduces redundancy in the update logic for both BaseModel and ClusterBaseModel, potentially resulting in duplicate download tasks when the download policy is modified.