Run e2e across Chromium, Firefox, and WebKit

Add Firefox and WebKit projects so the suite covers all three evergreen
engines, and install all three in CI. WebKit passes locally; Firefox is
verified in CI (its Playwright build will not spawn on the Windows dev
box, but launches fine on the Linux runner).

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

Author: githyperplexed

.github/workflows/ci.yml

@@ -30,5 +30,5 @@ jobs:
       - uses: actions/checkout@v6
       - uses: oven-sh/setup-bun@v2
       - run: bun install --frozen-lockfile
-      - run: bunx playwright install --with-deps chromium
+      - run: bunx playwright install --with-deps chromium firefox webkit
       - run: bun run test:e2e

playwright.config.ts

@@ -18,7 +18,11 @@ export default defineConfig({
 		baseURL: "http://localhost:5174",
 		trace: "on-first-retry"
 	},
-	projects: [{ name: "chromium", use: { ...devices["Desktop Chrome"] } }],
+	projects: [
+		{ name: "chromium", use: { ...devices["Desktop Chrome"] } },
+		{ name: "firefox", use: { ...devices["Desktop Firefox"] } },
+		{ name: "webkit", use: { ...devices["Desktop Safari"] } }
+	],
 	webServer: {
 		command: "bunx vite --config tests/e2e/fixture.vite.ts --port 5174 --strictPort",
 		url: "http://localhost:5174",