all: only display total input tokens

Knowing the cache reads and writes was mildly interesting for us,
but it is inside baseball, and our calculations ended up being a little wrong.
Streamline the UI and make the math right.

Co-Authored-By: sketch <hello@sketch.dev>
diff --git a/webui/src/web-components/sketch-timeline-message.test.ts b/webui/src/web-components/sketch-timeline-message.test.ts
index bc74202..d5c8dfb 100644
--- a/webui/src/web-components/sketch-timeline-message.test.ts
+++ b/webui/src/web-components/sketch-timeline-message.test.ts
@@ -149,9 +149,8 @@
   });
 
   await expect(component.locator(".message-usage")).toBeVisible();
-  await expect(component.locator(".message-usage")).toContainText("150"); // In
+  await expect(component.locator(".message-usage")).toContainText("200"); // In (150 + 50 cache)
   await expect(component.locator(".message-usage")).toContainText("300"); // Out
-  await expect(component.locator(".message-usage")).toContainText("50"); // Cache
   await expect(component.locator(".message-usage")).toContainText("$0.03"); // Cost
 });