Promote validation-gen tags to Stable

Promote the stability of the following tags defined in validation-gen/validator directory to Stable.
These tags were introduced in the API types (staging/src/k8s.io/api) in the following commits:

- k8s:enum (2025-10-15): 9020a17731 https://github.com/kubernetes/kubernetes/commit/9020a177318
- k8s:format (2025-09-16): 8606fa03dc https://github.com/kubernetes/kubernetes/commit/8606fa03dc7
- k8s:listMapKey (2025-07-16): 6a2d5a1e64 https://github.com/kubernetes/kubernetes/commit/6a2d5a1e644
- k8s:listType (2025-07-16): 6a2d5a1e64 https://github.com/kubernetes/kubernetes/commit/6a2d5a1e644
- k8s:maxItems (2025-09-18): 11df50453f https://github.com/kubernetes/kubernetes/commit/11df50453fc
- k8s:maxLength (2025-10-22): 6fa8cb4a99 https://github.com/kubernetes/kubernetes/commit/6fa8cb4a993
- k8s:minimum (2024-11-30): e08bbf254c https://github.com/kubernetes/kubernetes/commit/e08bbf254c4
- k8s:optional (2024-12-19): 0f4786536f https://github.com/kubernetes/kubernetes/commit/0f4786536f7
- k8s:required (2025-09-16): 8606fa03dc https://github.com/kubernetes/kubernetes/commit/8606fa03dc7
- k8s:subfield (2025-04-14): 229c6b13ca https://github.com/kubernetes/kubernetes/commit/229c6b13ca7
- k8s:unionMember (2025-10-23): 8a6b3caaa0 https://github.com/kubernetes/kubernetes/commit/8a6b3caaa0d
- k8s:zeroOrOneOfMember (2025-07-16): 6a2d5a1e64 https://github.com/kubernetes/kubernetes/commit/6a2d5a1e644
- k8s:item (2025-07-16): 6a2d5a1e64 https://github.com/kubernetes/kubernetes/commit/6a2d5a1e644

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/enum.go

@@ -194,7 +194,7 @@ func (etv *enumTagValidator) GetValidations(context Context, _ codetags.Tag) (Va
 func (etv *enumTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            etv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         etv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that a string type is an enum. All constant values of this type are considered values in the enum unless excluded using +k8s:enumExclude.",
 	}

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/format.go

@@ -120,7 +120,7 @@ func getFormatValidationFunction(format string) (FunctionGen, error) {
 func (ftv formatTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            ftv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         ftv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that a string field has a particular format.",
 		Payloads: []TagPayloadDoc{{ // Keep this list alphabetized.

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/item.go

@@ -249,7 +249,7 @@ func parseTypedValue(value string, argType codetags.ArgType) (any, codetags.Valu
 func (itv itemTagValidator) Docs() TagDoc {
 	doc := TagDoc{
 		Tag:            itv.TagName(),
-		StabilityLevel: Alpha,
+		StabilityLevel: Stable,
 		Scopes:         itv.ValidScopes().UnsortedList(),
 		Description: "Declares a validation for an item of a slice declared as a +k8s:listType=map. " +
 			"The item to match is declared by providing field-value pair arguments. All key fields must be specified.",

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/limits.go

@@ -79,7 +79,7 @@ func (maxLengthTagValidator) GetValidations(context Context, tag codetags.Tag) (
 func (mltv maxLengthTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            mltv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         mltv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that a string field has a limit on its length.",
 		Payloads: []TagPayloadDoc{{
@@ -137,7 +137,7 @@ func (maxItemsTagValidator) GetValidations(context Context, tag codetags.Tag) (V
 func (mitv maxItemsTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            mitv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         mitv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that a list has a limit on its size.",
 		Payloads: []TagPayloadDoc{{
@@ -187,7 +187,7 @@ func (minimumTagValidator) GetValidations(context Context, tag codetags.Tag) (Va
 func (mtv minimumTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            mtv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         mtv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that a numeric field has a minimum value.",
 		Payloads: []TagPayloadDoc{{

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/list.go

@@ -182,7 +182,7 @@ func (lttv listTypeTagValidator) GetValidations(context Context, tag codetags.Ta
 func (lttv listTypeTagValidator) Docs() TagDoc {
 	doc := TagDoc{
 		Tag:            lttv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         lttv.ValidScopes().UnsortedList(),
 		Description:    "Declares a list field's semantic type and ownership behavior. atomic: single ownership, set: shared ownership with uniqueness, map: shared ownership with key-based uniqueness.",
 		Payloads: []TagPayloadDoc{{
@@ -250,7 +250,7 @@ func (lmktv listMapKeyTagValidator) GetValidations(context Context, tag codetags
 func (lmktv listMapKeyTagValidator) Docs() TagDoc {
 	doc := TagDoc{
 		Tag:            lmktv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         lmktv.ValidScopes().UnsortedList(),
 		Description:    "Declares a named sub-field of a list's value-type to be part of the list-map key.",
 		Payloads: []TagPayloadDoc{{

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/required.go

@@ -309,10 +309,10 @@ func (rtv requirednessTagValidator) Docs() TagDoc {
 
 	switch rtv.mode {
 	case requirednessRequired:
-		doc.StabilityLevel = Beta
+		doc.StabilityLevel = Stable
 		doc.Description = "Indicates that a field must be specified by clients."
 	case requirednessOptional:
-		doc.StabilityLevel = Beta
+		doc.StabilityLevel = Stable
 		doc.Description = "Indicates that a field is optional to clients."
 	case requirednessForbidden:
 		doc.StabilityLevel = Alpha

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/subfield.go

@@ -132,9 +132,9 @@ func (stv subfieldTagValidator) GetValidations(context Context, tag codetags.Tag
 }
 
 func (stv subfieldTagValidator) Docs() TagDoc {
-	doc := TagDoc{
+	return TagDoc{
 		Tag:            stv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         stv.ValidScopes().UnsortedList(),
 		Description:    "Declares a validation for a subfield of a struct.",
 		Args: []TagArgDoc{{
@@ -150,5 +150,4 @@ func (stv subfieldTagValidator) Docs() TagDoc {
 		PayloadsType:     codetags.ValueTypeTag,
 		PayloadsRequired: true,
 	}
-	return doc
 }

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/union.go

@@ -156,7 +156,7 @@ func (umtv unionMemberTagValidator) GetValidations(context Context, tag codetags
 func (umtv unionMemberTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            umtv.TagName(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Scopes:         umtv.ValidScopes().UnsortedList(),
 		Description:    "Indicates that this field is a member of a union.",
 		Args: []TagArgDoc{{

staging/src/k8s.io/code-generator/cmd/validation-gen/validators/zeroorone.go

@@ -101,7 +101,7 @@ func (zmtv zeroOrOneOfMemberTagValidator) Docs() TagDoc {
 	return TagDoc{
 		Tag:            zmtv.TagName(),
 		Scopes:         zmtv.ValidScopes().UnsortedList(),
-		StabilityLevel: Beta,
+		StabilityLevel: Stable,
 		Description:    "Indicates that this field is a member of a zero-or-one-of union.",
 		Docs:           "A zero-or-one-of union allows at most one member to be set. Unlike regular unions, having no members set is valid.",
 		Warning:        "This tag should only be used on sets of list items, and never on struct fields directly.",