fix: display build timings when all timings are loaded (#15728)

- [Refetch timings until script timings are
present](https://github.com/coder/coder/commit/2181bec72b5334e5e15dc575d2234860be02920b)
- [Stay on loading state when agent script timings are
empty](https://github.com/coder/coder/commit/b16fad165c8733c60150b0dfce5df73ab2669e36)

Fix https://github.com/coder/coder/issues/15273

site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.stories.tsx

@@ -118,3 +118,11 @@ export const DuplicatedScriptTiming: Story = {
 		],
 	},
 };
+
+// Loading when agent script timings are empty
+// Test case for https://github.com/coder/coder/issues/15273
+export const LoadingWhenAgentScriptTimingsAreEmpty: Story = {
+	args: {
+		agentScriptTimings: undefined,
+	},
+};

site/src/modules/workspaces/WorkspaceTiming/WorkspaceTimings.tsx

@@ -58,15 +58,25 @@ export const WorkspaceTimings: FC<WorkspaceTimingsProps> = ({
 	].sort((a, b) => {
 		return new Date(a.started_at).getTime() - new Date(b.started_at).getTime();
 	});
-	const [isOpen, setIsOpen] = useState(defaultIsOpen);
-	const isLoading = timings.length === 0;
 
-	// All stages
+	const [isOpen, setIsOpen] = useState(defaultIsOpen);
+
+	// If any of the timings are empty, we are still loading the data. They can be
+	// filled in different moments.
+	const isLoading = [
+		provisionerTimings,
+		agentScriptTimings,
+		agentConnectionTimings,
+	].some((t) => t.length === 0);
+
+	// Each agent connection timing is a stage in the timeline to make it easier
+	// to users to see the timing for connection and the other scripts.
 	const agentStageLabels = Array.from(
 		new Set(
 			agentConnectionTimings.map((t) => `agent (${t.workspace_agent_name})`),
 		),
 	);
+
 	const stages = [
 		...provisioningStages,
 		...agentStageLabels.flatMap((a) => agentStages(a)),
@@ -120,7 +130,8 @@ export const WorkspaceTimings: FC<WorkspaceTimingsProps> = ({
 											: mergeTimeRanges(stageTimings.map(toTimeRange));
 
 									// Prevent users from inspecting internal coder resources in
-									// provisioner timings.
+									// provisioner timings because they were not useful to the
+									// user and would add noise.
 									const visibleResources = stageTimings.filter((t) => {
 										const isProvisionerTiming = "resource" in t;
 										return isProvisionerTiming