BUG: VMRule CRD injects empty `record: ""` / `alert: ""` into every rule

Describe the bug

Rule.Record and Rule.Alert in api/operator/v1beta1/vmrule_types.go carry +kubebuilder:default="".

The API server injects the empty counterpart field into every stored rule: alerting rules get record: "", recording rules get alert: "".

The applied manifest never contains these fields, so the live object never matches the source of truth. Diff-based GitOps tooling (Argo CD and equivalents) reports every application owning a VMRule as permanently OutOfSync.

Why the defaults are no longer needed

• #2258 added +listType=map with +listMapKey=record / +listMapKey=alert to RuleGroup.Rules, plus +kubebuilder:default="" on both fields. The defaults were required only because the API server rejects a list map key that has neither a default nor a required marker.
• #2379 removed the list-map markers from Rules again. The defaults were left behind.

With the list-map keys gone, nothing requires the defaults — they are residue, and their only remaining observable effect is the spurious diff.

Expected behavior

record and alert are omitempty optional fields. An applied VMRule should round-trip unchanged: no field the user did not set should appear on the stored object.

Version

First affected release is v0.73.0 (the markers are absent in v0.72.0) in v0.73.1, v0.74.0, v0.74.1 and v0.75.0-rc1, and on master.

Proposed fix

Drop +kubebuilder:default="" from Rule.Record and Rule.Alert, regen bundle. The doc comment on RuleGroup.Rules ("Rules are merged by record fields") is also stale after #2379 and can go in the same change.

Current workaround

Strip the defaults from the CRD bundle before applying, or add an ignoreDifferences entry in Argo CD for the field.