added custom header support and example extension

packages/coding-agent/src/core/extensions/loader.ts

@@ -90,6 +90,7 @@ function createNoOpUIContext(): ExtensionUIContext {
 		setStatus: () => {},
 		setWidget: () => {},
 		setFooter: () => {},
+		setHeader: () => {},
 		setTitle: () => {},
 		custom: async () => undefined as never,
 		setEditorText: () => {},

packages/coding-agent/src/core/extensions/runner.ts

@@ -65,6 +65,7 @@ const noOpUIContext: ExtensionUIContext = {
 	setStatus: () => {},
 	setWidget: () => {},
 	setFooter: () => {},
+	setHeader: () => {},
 	setTitle: () => {},
 	custom: async () => undefined as never,
 	setEditorText: () => {},

packages/coding-agent/src/core/extensions/types.ts

@@ -68,6 +68,9 @@ export interface ExtensionUIContext {
 	/** Set a custom footer component, or undefined to restore the built-in footer. */
 	setFooter(factory: ((tui: TUI, theme: Theme) => Component & { dispose?(): void }) | undefined): void;
 
+	/** Set a custom header component (shown at startup, above chat), or undefined to restore the built-in header. */
+	setHeader(factory: ((tui: TUI, theme: Theme) => Component & { dispose?(): void }) | undefined): void;
+
 	/** Set the terminal window/tab title. */
 	setTitle(title: string): void;
 

packages/coding-agent/src/core/sdk.ts

@@ -525,6 +525,7 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 			setStatus: () => {},
 			setWidget: () => {},
 			setFooter: () => {},
+			setHeader: () => {},
 			setTitle: () => {},
 			custom: async () => undefined as never,
 			setEditorText: () => {},