perf: build graph for next batch in parallel to keep GPU busy

This refactors the main run loop of the ollama runner to perform the main GPU
intensive tasks (Compute+Floats) in a go routine so we can prepare the next
batch in parallel to reduce the amount of time the GPU stalls waiting for the
next batch of work.

integration/max_queue_test.go

@@ -19,6 +19,8 @@ import (
 )
 
 func TestMaxQueue(t *testing.T) {
+	t.Skip("this test needs to be re-evaluated to use a proper embedding model")
+
 	if os.Getenv("OLLAMA_TEST_EXISTING") != "" {
 		t.Skip("Max Queue test requires spawning a local server so we can adjust the queue size")
 		return