fix(update): accept custom types from types.custom config (GH#hq-8hif1z)

The `bd update --type` command was rejecting custom types (like role, agent,
rig) even when configured via types.custom. The issue was that type validation
used IsValid() which only checks the 5 core types, ignoring custom types.

Changes:
- CLI (update.go): Use IsValidWithCustom() with types from config
- Storage (validators.go): Add validateIssueTypeWithCustom() function
- Storage (queries.go, transaction.go): Fetch and pass custom types

The error message now dynamically shows all valid types including custom ones.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/sqlite/validators.go

@@ -37,11 +37,17 @@ func validateStatusWithCustom(value interface{}, customStatuses []string) error
 	return nil
 }
 
-// validateIssueType validates an issue type value
+// validateIssueType validates an issue type value (built-in types only)
 func validateIssueType(value interface{}) error {
+	return validateIssueTypeWithCustom(value, nil)
+}
+
+// validateIssueTypeWithCustom validates an issue type value, allowing custom types.
+// Custom types are configured via bd config set types.custom "type1,type2,..."
+func validateIssueTypeWithCustom(value interface{}, customTypes []string) error {
 	if issueType, ok := value.(string); ok {
 		// Normalize first to support aliases like "enhancement" -> "feature"
-		if !types.IssueType(issueType).Normalize().IsValid() {
+		if !types.IssueType(issueType).Normalize().IsValidWithCustom(customTypes) {
 			return fmt.Errorf("invalid issue type: %s", issueType)
 		}
 	}
@@ -77,18 +83,29 @@ var fieldValidators = map[string]func(interface{}) error{
 	"estimated_minutes": validateEstimatedMinutes,
 }
 
-// validateFieldUpdate validates a field update value (built-in statuses only)
+// validateFieldUpdate validates a field update value (built-in statuses and types only)
 func validateFieldUpdate(key string, value interface{}) error {
-	return validateFieldUpdateWithCustomStatuses(key, value, nil)
+	return validateFieldUpdateWithCustom(key, value, nil, nil)
 }
 
 // validateFieldUpdateWithCustomStatuses validates a field update value,
 // allowing custom statuses for status field validation.
+// DEPRECATED: Use validateFieldUpdateWithCustom instead which also handles custom types.
 func validateFieldUpdateWithCustomStatuses(key string, value interface{}, customStatuses []string) error {
+	return validateFieldUpdateWithCustom(key, value, customStatuses, nil)
+}
+
+// validateFieldUpdateWithCustom validates a field update value,
+// allowing custom statuses and custom types for validation (GH#hq-8hif1z).
+func validateFieldUpdateWithCustom(key string, value interface{}, customStatuses, customTypes []string) error {
 	// Special handling for status field to support custom statuses
 	if key == "status" {
 		return validateStatusWithCustom(value, customStatuses)
 	}
+	// Special handling for issue_type field to support custom types
+	if key == "issue_type" {
+		return validateIssueTypeWithCustom(value, customTypes)
+	}
 	if validator, ok := fieldValidators[key]; ok {
 		return validator(value)
 	}