test: migrate e2e to Playwright and component test to Vitest browser mode

Replace Cypress with Playwright for the end-to-end suite and drop
@shellygo/cypress-test-utils in favour of a hand-written MaputnikDriver
page object that keeps the fluent then(...).shouldX() assertion style
(now async). The InputAutocomplete component test moves to Vitest browser
mode using the Playwright provider.

- e2e/maputnik-driver.ts: driver + MaputnikAssertable over Playwright
- e2e/{fixtures,coverage,global-setup,global-teardown}.ts: test fixture,
  istanbul coverage collection, and nyc report generation
- playwright.config.ts / vitest.config.ts
- Code coverage preserved: dev server is istanbul-instrumented, per-test
  window.__coverage__ is merged via nyc into coverage/coverage-final.json
- CI: Cypress jobs replaced with Playwright; docker e2e runs against the
  container via E2E_NO_WEBSERVER
- Remove Cypress deps, config and support files; update docs and .nycrc

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e/coverage.ts

@@ -0,0 +1,30 @@
+import fs from "node:fs";
+import path from "node:path";
+import type { Page } from "@playwright/test";
+
+const OUTPUT_DIR = path.resolve(process.cwd(), ".nyc_output");
+
+/**
+ * Reads the istanbul coverage object (injected by vite-plugin-istanbul) from the
+ * given page. Returns `null` when the page has not been instrumented.
+ */
+export async function readCoverage(page: Page): Promise<unknown | null> {
+  try {
+    return await page.evaluate(() => (window as unknown as { __coverage__?: unknown }).__coverage__ ?? null);
+  } catch {
+    // Page might be navigating/closed.
+    return null;
+  }
+}
+
+/**
+ * Persists a coverage chunk to `.nyc_output` so that `nyc report` can merge it.
+ * istanbul-lib-coverage (used by nyc) sums the hit counts across every file it
+ * finds, so writing one file per chunk is enough to accumulate coverage across
+ * navigations and tests.
+ */
+export function writeCoverage(coverage: unknown, id: string): void {
+  if (!coverage) return;
+  fs.mkdirSync(OUTPUT_DIR, { recursive: true });
+  fs.writeFileSync(path.join(OUTPUT_DIR, `playwright-${id}.json`), JSON.stringify(coverage));
+}