[GuiBoneVowt]

When an NPC shoots another NPC, NPC::shoot only applies the damage if (!dead_ && !invulnerable_), and those are the shooter's fields. The player → NPC path (NPCComponent::onPlayerGiveDamage) checks the target with npc->isInvulnerable(), which matches what NPC_SetInvulnerable is for ("Sets whether an NPC is invulnerable to damage").

On current master this means:

• an invulnerable NPC still takes damage from other NPCs;
• an invulnerable NPC can't damage other NPCs;
• shooting an NPC that is already dead still calls OnNPCTakeDamage.

This PR checks the target's dead and invulnerable state. The shooter's dead check stays, so a dead NPC still can't hurt anyone.

Testing

Windows, RelWithDebInfo, Win32 + ClangCL, on top of current master (72bf89c). Headless gamemode: two NPCs 2 units apart, NPC_Shoot with a Deagle and NPC_ENTITY_CHECK_NONE. Ran twice on each build, same results.

Case	master	this PR
Target invulnerable, shot once	health 100 → 53.7, OnNPCTakeDamage called	health stays 100, no callback
Shooter invulnerable, shoots once	target health stays 100	target health 100 → 53.7
Target shot three times	dies, OnNPCDeath once	same
Already-dead target shot once	OnNPCTakeDamage called	not called
NPC_Respawn, then shot three times	dies again, OnNPCDeath twice	same

Core of the test

new shooter = NPC_Create("shooter"), target = NPC_Create("target");
NPC_Spawn(shooter);
NPC_Spawn(target);
NPC_SetPos(shooter, 0.0, 0.0, 3.0);
NPC_SetPos(target, 2.0, 0.0, 3.0);

// A second later:
NPC_SetInvulnerable(target, true);
NPC_Shoot(shooter, WEAPON_DEAGLE, target, _:BULLET_HIT_TYPE_PLAYER, 2.0, 0.0, 3.0, 0.0, 0.0, 0.0, true, NPC_ENTITY_CHECK_NONE);
printf("%.1f", NPC_GetHealth(target)); // master: 53.7, this PR: 100.0

clang-format 13 with the repo's .clang-format: no changes.