feat(tui): add ASCII art banner on startup

src/frontends/tui/banner.ts

@@ -0,0 +1,32 @@
+// ASCII art banner for Flynn TUI startup
+
+/**
+ * Flynn ASCII art banner using block characters.
+ * Raw art lines without any color codes — callers apply their own styling.
+ */
+export const FLYNN_BANNER = `
+  ███████╗██╗     ██╗   ██╗███╗   ██╗███╗   ██╗
+  ██╔════╝██║     ╚██╗ ██╔╝████╗  ██║████╗  ██║
+  █████╗  ██║      ╚████╔╝ ██╔██╗ ██║██╔██╗ ██║
+  ██╔══╝  ██║       ╚██╔╝  ██║╚██╗██║██║╚██╗██║
+  ██║     ███████╗   ██║   ██║ ╚████║██║ ╚████║
+  ╚═╝     ╚══════╝   ╚═╝   ╚═╝  ╚═══╝╚═╝  ╚═══╝`;
+
+/**
+ * Returns the banner with ANSI color codes for terminal output.
+ * Uses orange (208) for the art and dim for the box frame.
+ */
+export function getColoredBanner(): string {
+  const orange = '\x1b[38;5;208m';
+  const reset = '\x1b[0m';
+
+  return `${orange}${FLYNN_BANNER}${reset}`;
+}
+
+/**
+ * Returns plain banner lines for use in Ink/React components.
+ * Each line is returned individually for flexible rendering.
+ */
+export function getBannerLines(): string[] {
+  return FLYNN_BANNER.split('\n').filter((line) => line.length > 0);
+}