fix STAY_NEAR_TARGET_ITEM

1. Allow "Stay near me" and "Stay near my target" to work even if the teams do not match
2. Allow "Stay near my target" to be issued regardless of team
3. Avoid divide-by-zero errors when running `ai_stay_near()`

Author: Goober5000

code/ai/aicode.cpp

@@ -11476,7 +11476,7 @@ void ai_stay_near()
 	else if (aip->submode_parm0 != 0) {
 		vec3d rand_vec, center_to_goal, center_to_objp;
 		auto goal_objp = &Objects[goal_objnum];
-		float max_dist = aip->submode_float0;
+		float max_dist = std::max(aip->submode_float0, 1.0f);
 
 		// Figure out a goal point to fly to
 		//	Make not all ships pursue same point.
@@ -11507,7 +11507,7 @@ void ai_stay_near()
 	else {
 		vec3d	rand_vec, goal_pos, vec_to_goal;
 		auto goal_objp = &Objects[goal_objnum];
-		float max_dist = aip->submode_float0;
+		float max_dist = std::max(aip->submode_float0, 1.0f);
 
 		//	Make not all ships pursue same point.
 		//	Calculate the seed from both shipnums so the same Pl_objp doesn't always choose the same spot

code/hud/hudsquadmsg.cpp

@@ -147,8 +147,9 @@ SCP_vector<player_order> Player_orders = {
 };
 
 const SCP_set<size_t> default_messages{ ATTACK_TARGET_ITEM , DISABLE_TARGET_ITEM , DISARM_TARGET_ITEM , PROTECT_TARGET_ITEM , IGNORE_TARGET_ITEM , FORMATION_ITEM , COVER_ME_ITEM , ENGAGE_ENEMY_ITEM , DEPART_ITEM , DISABLE_SUBSYSTEM_ITEM };
+// note: STAY_NEAR_TARGET_ITEM appears in both enemy and friendly sets
 const SCP_set<size_t> enemy_target_messages{ ATTACK_TARGET_ITEM , DISABLE_TARGET_ITEM , DISARM_TARGET_ITEM , IGNORE_TARGET_ITEM , STAY_NEAR_TARGET_ITEM , CAPTURE_TARGET_ITEM , DISABLE_SUBSYSTEM_ITEM };
-const SCP_set<size_t> friendly_target_messages{ PROTECT_TARGET_ITEM };
+const SCP_set<size_t> friendly_target_messages{ PROTECT_TARGET_ITEM , STAY_NEAR_TARGET_ITEM };
 const SCP_set<size_t> target_messages = []() {
 	SCP_set<size_t> setunion;
 	std::set_union(enemy_target_messages.cbegin(), enemy_target_messages.cend(), friendly_target_messages.cbegin(), friendly_target_messages.cend(), std::inserter(setunion, setunion.end()));
@@ -1319,11 +1320,6 @@ int hud_squadmsg_send_ship_command( int shipnum, int command, int send_message,
 
 		case STAY_NEAR_ME_ITEM:
 		case STAY_NEAR_TARGET_ITEM:
-
-			// cannot stay near a hostile ship(?)
-			if ( (command == STAY_NEAR_TARGET_ITEM) && (ship_team != target_team) )
-				break;
-
 			ai_mode = AI_GOAL_STAY_NEAR_SHIP;
 			ai_submode = -1;
 			message = MESSAGE_YESSIR;