ci: fix runner image (node:20), add Playwright smoke tests

- Change runner to node:20 (has bash) instead of node:20-alpine
- Add tests/smoke.spec.js: 7 tests covering title, welcome screen,
  COMARCA_PATHS count (43), Lluçanès/Moianès presence, and
  filter counts (coastal=12, interior=21, mountain=10)
- Add playwright.config.js
- Fix CI workflow: use 'serve' for static server, proper SSH key setup

tests/smoke.spec.js

@@ -0,0 +1,75 @@
+// smoke.spec.js — Basic smoke tests for comarques app
+// Runs against a static HTTP server (no DB required).
+// Playwright is invoked with chromium via npx.
+
+const { test, expect } = require('@playwright/test');
+
+const BASE = process.env.APP_URL || 'http://localhost:9090';
+
+test.describe('App loads', () => {
+  test('title is correct', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await expect(page).toHaveTitle(/Comarques de Catalunya/);
+  });
+
+  test('welcome screen is shown on first load', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    // Clear any existing player so we always land on welcome
+    await page.evaluate(() => localStorage.clear());
+    await page.reload();
+    const welcome = page.locator('#screen-welcome');
+    await expect(welcome).toBeVisible();
+  });
+});
+
+test.describe('comarca-paths.js', () => {
+  test('COMARCA_PATHS loads and has 43 entries', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await page.waitForTimeout(500);
+    const count = await page.evaluate(() => Object.keys(COMARCA_PATHS).length);
+    expect(count).toBe(43);
+  });
+
+  test('Lluçanès and Moianès have map paths', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await page.waitForTimeout(500);
+    const result = await page.evaluate(() => ({
+      llucanes: !!COMARCA_PATHS['Lluçanès'],
+      moianes:  !!COMARCA_PATHS['Moianès'],
+    }));
+    expect(result.llucanes).toBe(true);
+    expect(result.moianes).toBe(true);
+  });
+});
+
+test.describe('Filters', () => {
+  test('coastal filter returns 12 comarques', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await page.waitForTimeout(500);
+    const count = await page.evaluate(() => {
+      activeGroups = new Set(['coastal']);
+      return getActiveComarques().length;
+    });
+    expect(count).toBe(12);
+  });
+
+  test('interior filter returns 21 comarques', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await page.waitForTimeout(500);
+    const count = await page.evaluate(() => {
+      activeGroups = new Set(['interior']);
+      return getActiveComarques().length;
+    });
+    expect(count).toBe(21);
+  });
+
+  test('mountain filter returns 10 comarques', async ({ page }) => {
+    await page.goto(BASE + '/index.html');
+    await page.waitForTimeout(500);
+    const count = await page.evaluate(() => {
+      activeGroups = new Set(['mountain']);
+      return getActiveComarques().length;
+    });
+    expect(count).toBe(10);
+  });
+});