Serialise flags value

[dubstar-04]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.87%. Comparing base (2d5ccf4) to head (4724b81).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #317      +/-   ##
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+ Coverage   91.86%   91.87%   +0.01%     
==========================================
  Files         128      128              
  Lines        9350     9352       +2     
  Branches     1966     1966              
==========================================
+ Hits         8589     8592       +3     
+ Misses        685      684       -1     
  Partials       76       76              

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[Copilot]

Pull request overview

This PR makes Flags serialise to a plain numeric value so JSON-based flows preserve bitmask state when entities are copied, stringified, and reconstructed. In the codebase, this is especially relevant to clipboard/import-style round trips where flagged entities such as polylines and text rely on numeric flag values during reconstruction.

Changes:

• Add Flags.toJSON() so JSON.stringify() emits the numeric flag value instead of a nested { flags: ... } object.
• Document why numeric serialisation is needed for clipboard-style round trips.
• Add unit tests covering toJSON() directly and a basic JSON stringify/parse round trip for Flags.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
core/properties/flags.js	Adds numeric JSON serialisation for Flags instances.
test/properties/flags.test.js	Adds unit tests for direct and JSON round-trip serialisation of Flags.

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