feat(app): session timeline/turn rework (#13196)

Co-authored-by: David Hill <iamdavidhill@gmail.com>

packages/ui/src/components/text-shimmer.tsx

@@ -0,0 +1,36 @@
+import { For, createMemo, type ValidComponent } from "solid-js"
+import { Dynamic } from "solid-js/web"
+
+export const TextShimmer = <T extends ValidComponent = "span">(props: {
+  text: string
+  class?: string
+  as?: T
+  active?: boolean
+  stepMs?: number
+  durationMs?: number
+}) => {
+  const chars = createMemo(() => Array.from(props.text))
+  const active = () => props.active ?? true
+
+  return (
+    <Dynamic
+      component={props.as || "span"}
+      data-component="text-shimmer"
+      data-active={active()}
+      class={props.class}
+      aria-label={props.text}
+      style={{
+        "--text-shimmer-step": `${props.stepMs ?? 45}ms`,
+        "--text-shimmer-duration": `${props.durationMs ?? 1200}ms`,
+      }}
+    >
+      <For each={chars()}>
+        {(char, index) => (
+          <span data-slot="text-shimmer-char" aria-hidden="true" style={{ "--text-shimmer-index": `${index()}` }}>
+            {char}
+          </span>
+        )}
+      </For>
+    </Dynamic>
+  )
+}