feat: (devx/demo page) add flowchart expanded node page

[lee-treehouse]

📑 Summary

In issue #7502 we discuss a regression to node borders that has affected representing datastores in dataflow diagrams.

I wondered if it might be useful to have a dedicated flowchart shape (rails-rectangle or similar), rather than or as well as fixing the regression so borders can be customized to achieve the shape.

This PR doesn't do that :)

While I was wondering about adding new shapes, I realised i don't have an easy way to understand or visualise all the expanded node shapes that are mentioned here

So this page adds such a page, for developers, showing the expanded node shapes in their original and hand drawn versions.

No changeset, e2e tests requires as this is developer facing only.

📋 Tasks

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• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
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commit: 10bc6c5

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Build	Status	Details	Updated (UTC)
default (Inspect)	⚠️ Changes detected (Review)	2 changed	Apr 9, 2026, 9:41 AM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.33%. Comparing base (49938d6) to head (10bc6c5).
⚠️ Report is 6 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7510      +/-   ##
==========================================
- Coverage     3.33%   3.33%   -0.01%     
==========================================
  Files          535     536       +1     
  Lines        56238   56249      +11     
  Branches       820     820              
==========================================
  Hits          1876    1876              
- Misses       54362   54373      +11     

Flag	Coverage Δ
unit	3.33% <ø> (-0.01%)	⬇️

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