Rename constructor to game.New(game.Params) per styleguide

NewGame(Config) becomes New(Params), and Restore takes Params too, so
the package's primary type gets the canonical New() constructor with a
named-field Params struct (styleguide points 139, 159). cmd/rogue and
all tests updated; ARCHITECTURE.md constructor references corrected.
Pure rename, suite green.

game/save_test.go

@@ -29,7 +29,7 @@ func TestSaveRestoreRoundTrip(t *testing.T) {
 		t.Fatalf("saveFile: %v", saveErr)
 	}
 
-	h, err := Restore(path, Config{Term: &testTerm{}})
+	h, err := Restore(path, Params{Term: &testTerm{}})
 	if err != nil {
 		t.Fatalf("Restore: %v", err)
 	}
@@ -154,7 +154,7 @@ func TestRestoreRejectsWrongVersion(t *testing.T) {
 		t.Fatal(closeErr)
 	}
 
-	_, restoreErr := Restore(path, Config{})
+	_, restoreErr := Restore(path, Params{})
 	if restoreErr == nil {
 		t.Error("restore accepted an out-of-date save")
 	}