## Summary
- Add a Spall Liner toggle button to the Tankopedia model viewer, placed alongside the existing Calibrated Shells / Enhanced Armor buttons. It's only shown for tanks that can actually equip Spall Liner.
- The toggle reads/writes the same `Duel.protagonist.provisions` array as the Provisions tab, so both stay in sync automatically.
- If a provision slot is free, clicking equips Spall Liner immediately. If all slots are full, a popover shows icons with a shuffle arrow so you can pick which active provision to swap out in one step.
- Buttons use the same medium rounding as the consumable buttons on the tank page.
- When Spall Liner is equipped, the Dynamic Armor 3D viewer's click-damage tooltip now applies the same 20% HE damage reduction Spall Liner grants in-game.
- Refactored the hardcoded `-0.2` HE damage coefficient in `tankCharacteristics.ts` into a shared constant so the Compare tool and the 3D viewer use a single source of truth.
## Scope
This only affects the single-tank Tankopedia page. The Firepower stats table (the viewed tank's own outgoing gun damage) is intentionally untouched, since a defensive damage reduction would be semantically backwards there. The Dynamic Armor viewer's click tooltip is the only place a "damage taken by this tank" number exists, so that's where the reduction is wired in.
PrimaryArmorSceneComponent rebuilt its ShaderMaterial every render with null uniforms that were only set once on mount. Create it once with useState instead.
TrèsAbhi
Mark Greene