fix: bounds check, CanSet guard, and call.Failed on unpack error

- call.go: guard against struct fields > ABI output count (panic)
- call.go: check field.CanSet() before field.Set() (panic on unexported fields)
- caller.go: set call.Failed=true when CanFail=true and unpack fails

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

call.go

@@ -108,8 +108,14 @@ func (call *Call) Unpack(b []byte) error {
 	}
 
 	fieldCount := t.NumField()
+	if fieldCount > len(out) {
+		return fmt.Errorf("struct has %d fields but ABI returned %d values", fieldCount, len(out))
+	}
 	for i := 0; i < fieldCount; i++ {
 		field := t.Field(i)
+		if !field.CanSet() {
+			return fmt.Errorf("field %d (%s) is not settable (unexported?)", i, t.Type().Field(i).Name)
+		}
 		converted := abi.ConvertType(out[i], field.Interface())
 		field.Set(reflect.ValueOf(converted))
 	}

caller.go

@@ -85,6 +85,7 @@ func (caller *Caller) calls(opts *bind.CallOpts, calls ...*Call) ([]*Call, error
 		call.Failed = !result.Success
 		if err := call.Unpack(result.ReturnData); err != nil {
 			if call.CanFail {
+				call.Failed = true // mark as failed so callers don't need to inspect Outputs
 				log.Println(fmt.Errorf("failed to unpack call outputs at index [%d]: %v", i, err))
 				continue
 			}