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.
Add about to authenticatedMobilePages to capture an authenticated baseline
needed for regression detection during the Phase 3.5 about.vue migration.
Rename all auth-mobile snapshots from *-mobile to *-mobile-auth to avoid
name collision with the public loop's about-mobile snapshot.