6920: Fix Gantt chart crashes in Obsidian and browser

[darshanr0107]

📑 Summary

This PR fixes a crash in Gantt chart rendering caused by an Invalid array length RangeError. The issue occurred during axis and tick calculations
Resolves #6920

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Latest commit: d318f1a

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commit: d318f1a

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.57%. Comparing base (1c2a002) to head (d318f1a).
⚠️ Report is 15 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6945   +/-   ##
=======================================
  Coverage     3.56%   3.57%           
=======================================
  Files          473     474    +1     
  Lines        47198   47212   +14     
  Branches       728     730    +2     
=======================================
+ Hits          1684    1687    +3     
- Misses       45514   45525   +11     

Flag	Coverage Δ
unit	3.57% <100.00%> (+<0.01%)	⬆️

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Files with missing lines	Coverage Δ
packages/mermaid/src/diagrams/gantt/ganttDb.js	76.57% <100.00%> (+0.09%)	⬆️

... and 1 file with indirect coverage changes

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Changes approved	2 added	Sep 15, 2025, 7:47 AM

[Copilot]

Pull Request Overview

This PR fixes a crash in Gantt chart rendering caused by an Invalid array length RangeError when using numeric timestamps with dateFormat 'x' or 'X'. The fix adds proper handling for numeric timestamp parsing.

• Added numeric timestamp validation and parsing for dateFormat 'x' and 'X'
• Included comprehensive test coverage for both 'x' and 'X' dateFormat scenarios
• Created appropriate changeset documenting the bug fix

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/mermaid/src/diagrams/gantt/ganttDb.js	Adds numeric timestamp parsing logic for 'x' and 'X' dateFormats
cypress/integration/rendering/gantt.spec.js	Adds test cases to verify numeric timestamp handling
.changeset/moody-fans-try.md	Documents the bug fix in changeset

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