Testing: Blocks V2 and Field types e2e tests

[priethor]

What

Adds E2E tests for Block V3 and field types.

Why and How

• The Block V3 features (preview-only mode, sidebar fields, live preview updates) needed automated verification.
• Testing all field types end-to-end ensures the complete render → save → retrieve → display cycle works correctly across 20+ field types.

Testing Instructions

Run the new E2E tests:

npm run test:e2e -- tests/e2e/block-v3-features.spec.ts tests/e2e/all-field-types.spec.ts

[github-actions]

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Props priethor.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.60%. Comparing base (f21ac02) to head (f1b06df).
⚠️ Report is 1 commits behind head on trunk.

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk     #352      +/-   ##
============================================
- Coverage     51.97%   51.60%   -0.37%     
  Complexity     4410     4410              
============================================
  Files           298      298              
  Lines         39424    39424              
============================================
- Hits          20490    20345     -145     
- Misses        18934    19079     +145     

Flag	Coverage Δ
e2e-js	44.95% <ø> (+0.21%)	⬆️
e2e-php	39.04% <ø> (-0.54%)	⬇️
javascript	15.07% <ø> (ø)
phpunit	29.97% <ø> (ø)

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