Defender, Steelcreast and Bulwark no longer keep stances active when stunned/dead and display correct knockdown sprites.

[Venuska1117]

Requesting Testmerge for this PR, there might be unintended side-effects.

Feedback:

https://discord.com/channels/150315577943130112/1464087612796174501

Detached from: #12601

About the pull request

Makes castes such as Defender, Steelcrest and Bulwark to display their knockdown sprites when stunned by explosives (or any other strong source of damage) and make them lose stances like fortify and reflective shield.

Also updates some code to use traits and "better" logic.

Fixes: #8287
Fixes: #12562
This PR also solves unintentional issue presented in other PR: #11976

Explain why it's good for the game

Shows to other people like marines or xenos, that Defender, Steelcrest or Bulwark are stunned from explosive and are vulnerable, showing visual sprite of knockdown, this PR also makes them lose stance from explosives, they already get stunned by explosive during stances, it was just not visible (other than blood sprites or fire sprites).

As for stance removal, such as Fortify and Reflective, this was decided after noticing that, stunned fortified defender still keep its 65 armor, this should not have place in game, this also goes for other abilities, with this change, stunned "defensive" xenos should be easier to kill, and for them, easier to escape when it goes bad.

Testing Video

▶️ New Fortified Defender reaction to explosives:

This also works on steelcrest strain.

2026-07-03.18-14-57.mp4

Changelog

🆑 Venuska1117
balance: If Defender or Steelcrest is stunned, they lose their Fortify Stance.
balance: If Defender or Steelcrest is dead, they lose their Crest and Fortify Stance.
balance: If Bulwark is stunned, they lose their Reflective Stance.
balance: If Bulwark is dead, they lose their Encased Plates and Reflective Stance.
fix: Defender and Steelcrest now display "knockdown" sprite when stunned during lowered crest or fortify.
fix: Bulwark now display "knockdown" sprite when stunned during encased plates or reflective shield.
/:cl:

[cm13-github]

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[cm13-github]

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[cmss13-ci]

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[cm13-github]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[cm13-github]

Conflicts have been resolved. A maintainer will review the pull request shortly.

[cm13-github]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[cm13-github]

Conflicts have been resolved. A maintainer will review the pull request shortly.

[cmss13-ci]

This PR has been inactive for long enough to be automatically marked as stale. This means it is at risk of being auto closed in ~ 7 days, please address any outstanding review items and ensure your PR is finished, if these are all true and you are auto-staled anyway, you need to actively ask maintainers if your PR will be merged. Once you have done any of the previous actions then you should request a maintainer remove the stale label on your PR, to reset the stale timer. If you feel no maintainer will respond in that time, you may wish to close this PR youself, while you seek maintainer comment, as you will then be able to reopen the PR yourself