[YevheniiKotyrlo]

What is this?

In Jest's CI mode (--ci, on by default when Jest detects a CI environment), toMatchImageSnapshot now fails when its snapshot does not exist, and saves the received image beside it as <name>-actual.png. Until now it wrote the snapshot and passed on CI too, so a run without committed snapshots compared nothing and a wrong capture could not fail it (#198). With CI=true and no committed snapshots, the playground's web suite passes on main and writes both specs' snapshots; on this branch the two specs fail with:

New snapshot was not written: src/tests/normal/ui/image_snapshots/chromium/out-of-bounds.png does not exist, and missing snapshots are not written in CI mode. Received image saved at src/tests/normal/ui/image_snapshots/chromium/out-of-bounds-actual.png; commit it as src/tests/normal/ui/image_snapshots/chromium/out-of-bounds.png, or run without CI mode (--ci=false) on a machine with this device and commit the snapshot it writes.

How does it work?

The session hands the bridge Jest's updateSnapshot state. When it is "none", CI mode's value, a missing image snapshot is not written and the match fails; outside CI mode, or with --ci=false, it is written as before, and so it is for a createHarnessBridge context that names no state. The received and diff images take the whole snapshot name, so a name holding .png keeps it. Like Jest's own snapshot matchers and jest-image-snapshot, toMatchImageSnapshot now refuses .not, which would turn that failure into a pass. The UI testing guide gets a "Creating snapshots" section and says .not is refused, the CLI reference lists --ci, and the repository ignores the failure images saved beside committed snapshots.

The playground's screenshot and out-of-bounds specs need committed baselines now, so this PR adds the ones CI's Android emulator, iOS simulator and headless Chromium capture. Android's out-of-bounds baseline shows the row's ten squares, which the app draws with one copy of react-native in the bundle, as it has since #227. On my fork, CI's E2E jobs on the current main with this PR pass both specs against these baselines on Android (run) and web (run); GitHub found no macOS runner for the iOS job, which last passed them on 9a505a8 (run).

Why is this useful?

A CI run now fails where it used to pass while comparing nothing: a snapshot that was never committed, or a capture that went wrong, shows up as a failed test with the received image saved for review.

Fixes #198

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