bug/7471: fix gantt font size and auto scale the barHeight and allow gantt to take themeVariables

[ankithapai]

📑 Summary

Fixed Gantt font-size handling, enabled automatic barHeight scaling, and allowed Gantt to consume themeVariables.
Resolves #7471

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commit: 5cfc1bd

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Codecov Report

❌ Patch coverage is 0% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.34%. Comparing base (2b938d0) to head (5cfc1bd).

Files with missing lines	Patch %	Lines
...ckages/mermaid/src/diagrams/gantt/ganttRenderer.js	0.00%	61 Missing ⚠️
packages/mermaid/src/diagrams/gantt/styles.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7537      +/-   ##
==========================================
- Coverage     3.34%   3.34%   -0.01%     
==========================================
  Files          524     524              
  Lines        55392   55445      +53     
  Branches       795     795              
==========================================
  Hits          1853    1853              
- Misses       53539   53592      +53     

Flag	Coverage Δ
unit	3.34% <0.00%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
packages/mermaid/src/diagrams/gantt/styles.js	0.00% <0.00%> (ø)
...ckages/mermaid/src/diagrams/gantt/ganttRenderer.js	0.00% <0.00%> (ø)

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Build	Status	Details	Updated (UTC)
default (Inspect)	⚠️ Changes detected (Review)	48 changed	Apr 7, 2026, 2:53 AM