docs: separate request and response batching guidance

[eventhorizon-cli]

Summary

• Split README API guidance into request-only and request/response sections.
• Keep the root English, root Chinese, and NuGet package README aligned.
• Render and reference the internal dispatch diagram as PNG in both root READMEs.

Validation

• Built samples/RequestBatcher.Deduplication/RequestBatcher.Deduplication.csproj in Release mode.
• Packed src/RequestBatcher/RequestBatcher.csproj and verified its embedded README contains the separated API sections.
• Checked all README content-diagram references resolve to local PNG assets.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.49%. Comparing base (4a8ea0d) to head (5e631ff).

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #4   +/-   ##
=======================================
  Coverage   90.49%   90.49%           
=======================================
  Files          15       15           
  Lines         747      747           
  Branches      106      106           
=======================================
  Hits          676      676           
  Misses         42       42           
  Partials       29       29           

☔ 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.