[srtaalej]

Summary

This pull request updates the remaining Block Kit Builder links from api.slack.com/tools/block-kit-builder to app.slack.com/block-kit-builder.

• app.slack.com/block-kit-builder is already used elsewhere in these docs (e.g. creating-an-app.md, the modals and order-confirmation tutorials).
• Updates the English and Japanese message-sending.md and shortcuts.md pages.

Testing

• Open each updated link and confirm it opens the Block Kit Builder in your workspace.
• Preview the Sending messages and Listening to shortcuts docs pages and confirm the links render.

Category

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.57%. Comparing base (7dd4bb4) to head (ab307d5).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1605   +/-   ##
=======================================
  Coverage   91.57%   91.57%           
=======================================
  Files         228      228           
  Lines        7285     7285           
=======================================
  Hits         6671     6671           
  Misses        614      614           

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[zimeg]

🔗 @srtaalej LGTM! Thanks for pointing these at the new Block Kit Builder home.