Add Playwright E2E suite against the built dist/

Pin @playwright/test 1.62.0 (matches the cached chromium
revision) and serve dist/ via python3 http.server, so the
deployed artifact is what gets tested. Covers page load,
terminal commands, vim mode, achievements, and the nav menu.
Ignore node_modules, test-results, playwright-report, and the
phased-execution runtime scratch (.agents/phase-sessions,
pipeline.log).

tests/e2e/helpers.js

@@ -0,0 +1,30 @@
+// Shared helpers for the fake-terminal E2E tests.
+//
+// Desktop interaction model (see src/script.js + src/terminal.js):
+// the hero section overlays the rack background, so the terminal is opened
+// by clicking the hero (outside of any .btn). That focuses the hidden
+// <input> inside .terminal-display, and all keystrokes go there.
+
+/** Click the hero to expand the terminal and focus its hidden input. */
+async function openTerminal(page) {
+    await page.locator('#hero h1').click();
+    await page.waitForSelector('.terminal-display.grown', { timeout: 5000 });
+}
+
+/** Type a command into the focused terminal and press Enter. */
+async function typeCommand(page, cmd) {
+    await page.keyboard.type(cmd);
+    await page.keyboard.press('Enter');
+}
+
+/** The current (last) line of the terminal output. */
+function currentPromptLine(page) {
+    return page.locator('.terminal-content > div').last();
+}
+
+/** All rendered terminal lines. */
+function terminalLines(page) {
+    return page.locator('.terminal-content > div');
+}
+
+module.exports = { openTerminal, typeCommand, currentPromptLine, terminalLines };