feat(ai): per-NPC npc:set_visible_enemy_bias selection lever

[damiansirbu]

Summary

Adds npc:set_visible_enemy_bias(actor_bias, npc_bias) on the stalker enemy manager. It overrides the two selection terms in CEnemyManager::evaluate() that favour whoever can see the NPC. actor_bias replaces the 900 subtracted when the actor sees the NPC. npc_bias replaces the 300 subtracted when another NPC sees it. Each arg is independent. A negative one keeps that side vanilla. A script can reduce the player magnet, the 3x pull the actor gets, so NPCs stop converging on the player. It can also retune per-NPC threat weighting. Nothing changes without a consumer.

Use cases

The bias gives an enemy that can see the NPC a large selection bonus. The actor bonus is 3x an NPC bonus, so squads converge on the player. A combat-fairness or threat-awareness mod sets it per-NPC to level the field, for example actor_bias equal to npc_bias. It can also weight toward the real threat.

Performance

No Lua runs on the path. The change adds two ternary reads per candidate.

Constraints

Per-object state lives on CEnemyManager and is not serialized. Re-set it on net_spawn, the same as set_vision_speed. Each arg is independent. A negative one keeps that side vanilla. A value of 0 removes the pull.

Files

• enemy_manager.cpp: fields, ctor init, setter, the two evaluate reads.
• enemy_manager.h: fields and setter declaration.
• script_game_object.h: declaration.
• script_game_object3.cpp: the bind with a CCustomMonster cast and error log, plus the enemy_manager.h include.
• script_game_object_script3.cpp: the .def next to set_vision_speed.
• gamedata/scripts/lua_help_ex.script: the manifest entry.

Lua usage

npc:set_visible_enemy_bias(300, -1)  -- player pulls like a regular NPC, npc side stays vanilla
npc:set_visible_enemy_bias(0, -1)    -- no artificial pull toward the player

Testing

Built locally at DX11 with 0 errors. Deployed and probed on the Cordon field. On a blind-spot NPC, set_visible_enemy_bias(0, 0) removes the 900 actor term:

[HITSET] actor_bias=900 | YOU YouseeN=true cost=8210.3 | match=true
[BIAS]   actor_bias=0   | YOU YouseeN=true cost=9112.1 | match=true

The actor cost rises by 900. That 900 is the removed magnet. The reconstruction with bias set to 0 matches the engine, so the row reads match=true. Once the pull is off, a competing enemy becomes selectable where the 900 term dominated before. Later samples can show the engine holding the prior target as a marginally better competitor appears. That is enemy-change inertia, the ENEMY_INERTIA_TIME window. The scoring change itself is exact.