chore: bump main version ref too now

[sicoyle]

Description

update main version ref now that 1.18 branch is out there

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #[issue number]

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[Copilot]

Pull request overview

Updates the repository’s single source-of-truth VERSION file to reflect the next development version on main now that the 1.18 release branch exists.

Changes:

• Bump VERSION from 1.18.0.dev to 1.19.0.dev.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.46%. Comparing base (bffb749) to head (25ba435).
⚠️ Report is 132 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1040      +/-   ##
==========================================
- Coverage   86.63%   82.46%   -4.17%     
==========================================
  Files          84      146      +62     
  Lines        4473    14501   +10028     
==========================================
+ Hits         3875    11958    +8083     
- Misses        598     2543    +1945     

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