Fix Hydrakin Plasma & Tritium Metabolism

[rebaserHEAD]

About the PR

Cleans up two longstanding inconsistencies in the Hydrakin gas-metabolism block in Resources/Prototypes/Reagents/gases.yml:

• Plasma & Tritium TOX icon: The Toxins alert was raised at >=1.5u in the lung even though the poison HealthChange already excludes Hydrakin. Added the same OrganType: Hydrakin, shouldHave: false guard to both AdjustAlert effects so the UI matches the actual damage state.
• Inhaled Tritium radiation: Inhaling Tritium dealt 1 Radiation/tick to Hydrakin with no species exclusion, contradicting the Hydrakin guidebook's "unique gases have mostly positive effect" claim. Added the same Hydrakin exclusion to that HealthChange. The bloodstream Poison-group radiation (3/tick, fires when Tritium is injected/drunk/touched) is intentionally left intact — shooting up radioactive isotopes should still hurt.

Why / Balance

Hydrakin already get an Oxygenate carve-out for all of Plasma/Tritium/Frezon/N2O/BZ/Healium/Nitrium/Pluoxium and are excluded from the poison damage on Plasma & Tritium. The lore (iceworld with frezon-heavy atmosphere, "capable of breathing all gases") and the in-game guidebook page both already promise this — the missing carve-outs on AdjustAlert and the inhaled-radiation HealthChange were holes in that contract, not intended balance. No new Hydrakin capabilities are being added; existing ones are just being made internally consistent.

Media

N/A — fix for an alert icon and an unintended damage tick. No visual content.

Requirements

• I have read relevant guidelines/documentation to this PR found on our devwiki.
• I have added media to this PR or it does not require an ingame showcase.
• I can confirm this PR contains either no AI-generated content, or AI-generated content that meets our guidelines.

How to test

1. Spawn as a Hydrakin.
2. Fill internals with a Plasma or Tritium tank and breathe from it (or stand in a plasma/trit-flooded room with no oxygen mask).
3. Confirm the TOX icon no longer appears in the alert column.
4. Run a health analyzer — confirm 0 Poison damage on both gases and 0 Radiation damage on Tritium inhalation.
5. As a control, inject Tritium directly into the bloodstream (e.g. syringe) and confirm Radiation damage still accrues.

Breaking changes

None. Pure YAML condition additions on existing effects; no prototype renames, no public API changes.

Changelog
🆑

• fix: Hydrakin no longer get a toxin warning when breathing plasma or tritium.
• fix: Hydrakin no longer take radiation damage from inhaling tritium. Injecting it still hurts.