feat: Add components to show steps in the copilot thinking process (#11530)

This PR adds the components for new Copilot UI
- Added a Header component
- Added a thinking block.
- Update the outline on copilot input

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

app/javascript/dashboard/components-next/copilot/CopilotHeader.story.vue

@@ -0,0 +1,21 @@
+<script setup>
+import CopilotHeader from './CopilotHeader.vue';
+</script>
+
+<template>
+  <Story
+    title="Captain/Copilot/CopilotHeader"
+    :layout="{ type: 'grid', width: '800px' }"
+  >
+    <!-- Default State -->
+    <Variant title="Default State">
+      <CopilotHeader />
+    </Variant>
+
+    <!-- With New Conversation Button -->
+    <Variant title="With New Conversation Button">
+      <!-- eslint-disable-next-line vue/prefer-true-attribute-shorthand -->
+      <CopilotHeader :has-messages="true" />
+    </Variant>
+  </Story>
+</template>