Merge pull request #2976 from wellsgz/codex/aws-claude-sonnet-4-6

feat(aws): add claude-sonnet-4-6 Bedrock mapping and cross-region support

relay/channel/aws/constants.go

@@ -14,6 +14,7 @@ var awsModelIDMap = map[string]string{
 	"claude-opus-4-20250514":     "anthropic.claude-opus-4-20250514-v1:0",
 	"claude-opus-4-1-20250805":   "anthropic.claude-opus-4-1-20250805-v1:0",
 	"claude-sonnet-4-5-20250929": "anthropic.claude-sonnet-4-5-20250929-v1:0",
+	"claude-sonnet-4-6":          "anthropic.claude-sonnet-4-6",
 	"claude-haiku-4-5-20251001":  "anthropic.claude-haiku-4-5-20251001-v1:0",
 	"claude-opus-4-5-20251101":   "anthropic.claude-opus-4-5-20251101-v1:0",
 	"claude-opus-4-6":            "anthropic.claude-opus-4-6-v1",
@@ -75,6 +76,11 @@ var awsModelCanCrossRegionMap = map[string]map[string]bool{
 		"ap": true,
 		"eu": true,
 	},
+	"anthropic.claude-sonnet-4-6": {
+		"us": true,
+		"ap": true,
+		"eu": true,
+	},
 	"anthropic.claude-opus-4-5-20251101-v1:0": {
 		"us": true,
 		"ap": true,