Add list-tests protocol message, test subcommands, extract test handlers

lib/client/client.go

@@ -117,6 +117,10 @@ func (c *Client) Log() (*ResponseLog, error) {
 	return first(roundTrip[ResponseLog](c, &RequestLog{}))
 }
 
+func (c *Client) ListTests() (*ResponseListTests, error) {
+	return first(roundTrip[ResponseListTests](c, &RequestListTests{}))
+}
+
 func (c *Client) Test(name string) (*ResponseTest, error) {
 	return first(roundTrip[ResponseTest](c, &RequestTest{Name: name}))
 }