Coalesce nil additional emails to empty array

The MCP Profile schema declares additional_email_addresses as a
required, non-nullable array, but NewProfile passed the mail.Addrs
value through unchanged. A profile with no extra emails has a nil
slice, which marshals to JSON null and fails tool output validation
with "type: null, want array".

Default the nil slice to an empty mail.Addrs so the marshalled output
always honors the strict array schema.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/server/api/mcp/v1/types/profile.go

@@ -14,15 +14,23 @@
 
 package types
 
-import "go.probo.inc/probo/pkg/coredata"
+import (
+	"go.probo.inc/probo/pkg/coredata"
+	"go.probo.inc/probo/pkg/mail"
+)
 
 func NewProfile(p *coredata.MembershipProfile) *Profile {
+	additionalEmailAddresses := p.AdditionalEmailAddresses
+	if additionalEmailAddresses == nil {
+		additionalEmailAddresses = mail.Addrs{}
+	}
+
 	return &Profile{
 		ID:                       p.ID,
 		OrganizationID:           p.OrganizationID,
 		FullName:                 p.FullName,
 		EmailAddress:             p.EmailAddress,
-		AdditionalEmailAddresses: p.AdditionalEmailAddresses,
+		AdditionalEmailAddresses: additionalEmailAddresses,
 		Kind:                     p.Kind,
 		Source:                   p.Source,
 		State:                    p.State,