Refactor snackbar locators

[Infinite-Null]

What?

Part of: #778

This PR standardizes the way we locate snackbar components in our E2E tests by migrating from CSS class selectors to the component's built-in data-test-id.

Why?

The Gutenberg snackbar component already provides data-test-id="snackbar", but we weren't utilizing it consistently. Previously, we were querying .components-snackbar__content. Moving to getByTestId aligns with our testing best practices.

How?

• Replaced instances of page.locator( '.components-snackbar__content' ) with page.getByTestId( 'snackbar' ).
• Updated assertions in settings.spec.js to correctly filter and verify the snackbar visibility using the new test ID.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Sonnet 4.6
Used for: Code review, PR description

Testing Instructions

Verify that CI passes, or run the updated E2E test locally:

npm run test:e2e tests/e2e/specs/admin/settings.spec.js

Changelog Entry

Developer - Standardize E2E snackbar locators to use data-test-id.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Infinite-Null <ankitkumarshah@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.04%. Comparing base (f006132) to head (1ba23c3).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #860   +/-   ##
==========================================
  Coverage      77.04%   77.04%           
  Complexity      2231     2231           
==========================================
  Files            103      103           
  Lines           9214     9214           
==========================================
  Hits            7099     7099           
  Misses          2115     2115           

Flag	Coverage Δ
unit	77.04% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.