Link open source practice from principles

[AyobamiH]

Summary

• link the existing Open Source practice from the engineering principles
• surface both areas covered by that practice: coding in the open and open source dependency licence obligations
• place the link in Create knowledge, beside the existing guidance about text in public repositories

Why

Issue #348 identifies that the Open Source practice is difficult to discover. The current principles page mentions open source repositories but does not link to the practice. This change adds one internal navigation link and a concise description without duplicating the detailed licensing guidance.

Validation

Validated the exact PR head, af0f28e, against base 02563df in GitHub Actions run 33190064128:

• verified a one-commit, one-file diff and ran git diff --check origin/main...HEAD
• ran BRANCH_NAME=main scripts/markdown-check-format.sh
• confirmed the relative target practices/open-source.md exists and is linked exactly once from principles.md
• confirmed the summary matches the practice page's coding-in-the-open and dependency-licensing guidance
• confirmed a clean tracked working tree

The upstream SonarCloud quality gate passed for this PR head. The upstream Check Markdown Format run is currently action_required and has not executed any jobs; it still requires maintainer approval.

Closes #348

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud