Sync 0.5.1 release back to develop

[Str4vinci]

Now that 0.5.1 is tagged, published, and released, this brings the release commit back onto develop so the two branches stop diverging. It is the last step of the release checklist and carries nothing that was not already reviewed in #117.

Summary

Synchronize the completed BREOS 0.5.1 release from main back into develop.

This carries only the reviewed release metadata from PR #117:

• package, lockfile, and citation version 0.5.1 dated 2026-08-11
• the Unreleased changelog section closed as [0.5.1] - 2026-08-11
• roadmap cleanup status restated for the 0.5.1 deprecation window and 0.6.0 removals
• validation baseline and report regenerated on 0.5.1 — stamps only, every number unchanged
• Python 3.14 recorded as a required release gate alongside Python 3.11–3.13

No source, simulation, or public result changes.

Release outcome

• PyPI: breos 0.5.1 published via trusted publishing and verified by a clean-environment install
• GitHub Release: https://github.com/Str4vinci/breos/releases/tag/v0.5.1
• tag v0.5.1 points at 62ab4f4 on main