Unify branding: VT323 logotype across website, TUI, and OAuth pages

- Add VT323 ASCII art logo to logo.mjs as single source of truth
- Website nav and hero use VT323 font via AsciiLogo.astro component
- TUI header and CLI help render the ASCII logo with block-centered alignment
- OAuth callback pages (Pi and alphaXiv) show branded feynman logotype
- Auto-set recommended model after provider login

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ui/terminal.ts

@@ -1,3 +1,5 @@
+import { FEYNMAN_ASCII_LOGO } from "../../logo.mjs";
+
 const RESET = "\x1b[0m";
 const BOLD = "\x1b[1m";
 const DIM = "\x1b[2m";
@@ -40,6 +42,17 @@ export function printSection(title: string): void {
 	console.log(paint(`◆ ${title}`, TEAL, BOLD));
 }
 
+export function printAsciiHeader(subtitleLines: string[] = []): void {
+	console.log("");
+	for (const line of FEYNMAN_ASCII_LOGO) {
+		console.log(paint(`  ${line}`, TEAL, BOLD));
+	}
+	for (const line of subtitleLines) {
+		console.log(paint(`  ${line}`, ASH));
+	}
+	console.log("");
+}
+
 export function printPanel(title: string, subtitleLines: string[] = []): void {
 	const inner = 53;
 	const border = "─".repeat(inner + 2);