gui: Keep short deviceID length consistent + xrefs (fixes #9313) (#9314)

Making short deviceID length consistent and referencing to protocol file
for future-proof edits. Closes #9313.

lib/protocol/deviceid.go

@@ -14,7 +14,8 @@ import (
 )
 
 const (
-	DeviceIDLength      = 32
+	DeviceIDLength = 32
+	// keep consistent with shortIDStringLength in gui/default/syncthing/app.js
 	ShortIDStringLength = 7
 )
 

lib/protocol/deviceid_test.go

@@ -84,6 +84,7 @@ func TestShortIDString(t *testing.T) {
 	id, _ := DeviceIDFromString(formatted)
 
 	sid := id.Short().String()
+	// keep consistent with ShortIDStringLength in lib/protocol/deviceid.go
 	if len(sid) != 7 {
 		t.Errorf("Wrong length for short ID: got %d, want 7", len(sid))
 	}