fix(shell-docs): restore stripped import lines in reference docs

The initial shell-docs content-import left 21 reference pages with missing
import statements: 8 component pages had empty `## Import` code fences, and
13 hook pages had `## Signature` fences whose leading `import { X } from
"@copilotkit/react-core/v2";` line was stripped.

This commit restores the import(s) in the Import and Signature fences only.
Usage examples and other code blocks are intentionally not touched.

- 8 components: fill empty Import fence with named (or default for
  CopilotChatView) import + styles.css side-effect import
- 13 hooks: prepend import line(s) at the top of the Signature fence.
  - useComponent: 3 imports (z, type ComponentType, useComponent)
  - useRenderTool: imports injected into both Wildcard and Named overload fences
  - useCopilotChatConfiguration: imports injected into both Provider and
    hook ### Signature subblocks

Author: samjulien

showcase/shell-docs/src/content/reference/components/CopilotChat.mdx

@@ -12,7 +12,8 @@ description: "High-level chat component that connects an agent to a chat view"
 ## Import
 
 ```tsx
-
+import { CopilotChat } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotChatAssistantMessage.mdx

@@ -10,7 +10,8 @@ description: "Component for displaying assistant messages with Markdown, tool ca
 ## Import
 
 ```tsx
-
+import { CopilotChatAssistantMessage } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotChatInput.mdx

@@ -12,7 +12,8 @@ The component operates in three modes: `"input"` (default text entry), `"transcr
 ## Import
 
 ```tsx
-
+import { CopilotChatInput } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotChatMessageView.mdx

@@ -10,7 +10,8 @@ description: "Component for rendering a list of chat messages"
 ## Import
 
 ```tsx
-
+import { CopilotChatMessageView } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotChatUserMessage.mdx

@@ -10,7 +10,8 @@ description: "Component for displaying user-authored messages with branch naviga
 ## Import
 
 ```tsx
-
+import { CopilotChatUserMessage } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotChatView.mdx

@@ -12,7 +12,8 @@ Every visual piece of `CopilotChatView` is exposed as a **slot**, so you can rep
 ## Import
 
 ```tsx
-
+import CopilotChatView from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 <Callout type="info">

showcase/shell-docs/src/content/reference/components/CopilotPopup.mdx

@@ -12,7 +12,8 @@ See [`CopilotSidebar`](/reference/components/CopilotSidebar) for a sidebar varia
 ## Import
 
 ```tsx
-
+import { CopilotPopup } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/components/CopilotSidebar.mdx

@@ -12,7 +12,8 @@ See [`CopilotPopup`](/reference/components/CopilotPopup) for a popup variant of
 ## Import
 
 ```tsx
-
+import { CopilotSidebar } from "@copilotkit/react-core/v2";
+import "@copilotkit/react-core/v2/styles.css";
 ```
 
 ## Props

showcase/shell-docs/src/content/reference/hooks/useAgent.mdx

@@ -12,6 +12,8 @@ description: "React hook for accessing AG-UI agent instances"
 ## Signature
 
 ```tsx
+import { useAgent } from "@copilotkit/react-core/v2";
+
 function useAgent(options?: UseAgentProps): { agent: AbstractAgent };
 ```
 

showcase/shell-docs/src/content/reference/hooks/useAgentContext.mdx

@@ -12,6 +12,8 @@ Update the incoming context object to refresh what the agent sees. This is the v
 ## Signature
 
 ```tsx
+import { useAgentContext } from "@copilotkit/react-core/v2";
+
 function useAgentContext(context: AgentContextInput): void;
 ```