Bug:Fix bitwise AND typo in sipnet.c

[Labreo]

Summary

• Motivation: The current logic for calcRootAndWoodFluxes() has a bug where it uses bitwise operation(&) for boolean comparison instead of (&&).
• What: Added && instead of & to add boolean logic.

How to test

Steps to reproduce and verify the change locally:

make
cd tests/smoke/<new-or-updated-test> ../../sipnet -i sipnet.in

Related issues

• Fixes # (or "Relates to #N" if this is not a resolution of that ticket)

Checklist

• Tests added for new features
• Documentation updated (if applicable)
• docs/CHANGELOG.md updated with noteworthy changes
• Code formatted with clang-format (run git clang-format if needed)
• Requested review from at least one CODEOWNER

For model structure changes:

• Removed \fraktur font formatting from docs/model-structure.md for implemented features

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Note: See CONTRIBUTING.md for additional guidance. This repository uses automated formatting checks; if the pre-commit hook blocks your commit, run git clang-format to format staged changes.

[Alomir]

Looks good, thanks!