build(playwright): drop OS suffix from snapshot path

Visual baselines were generated as chromium-darwin.png on macOS; CI on
Linux looked for chromium-linux.png and every test failed with
"snapshot doesn't exist". Override snapshotPathTemplate to omit the
platform suffix so darwin and linux share the same baseline. Pixel
diffs from font hinting are an accepted trade-off — visual regression
gives signal for big visual breaks, not 1-pixel differences.

Existing 26 baselines renamed from *-chromium-darwin.png to
*-chromium.png to match.

playwright.config.js

@@ -7,6 +7,7 @@ export default defineConfig({
   testDir: "./e2e",
   outputDir: "e2e/test-results",
   snapshotDir: "e2e/__screenshots__",
+  snapshotPathTemplate: "{snapshotDir}/{testFileDir}/{testFileName}-snapshots/{arg}-{projectName}{ext}",
   fullyParallel: false,
   forbidOnly: !!process.env.CI,
   retries: process.env.CI ? 1 : 1,