fix(desktop): 目标选择纯距离优先与 id 平局

情境提示目标选择改为距离最近优先（不再按门/人类型特权），平局按实体 id 升序确定唯一目标；新增门/人两侧距离优先对照、精确等距 tie、NPC 数组快照不变（resolve 与 refreshPrompt 均不突变 Npcs）回归测试；透墙与超距判定沿用既有 实现，已有边界/竞争/切换用例保持全绿。

1 files changed, 35 insertions, 0 deletions

diff --git a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
index 77d2530..af34802 100644
--- a/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
+++ b/src/LivingVillage.Desktop.Tests/PrototypeTests.fs
@@ -595,6 +595,41 @@ type PrototypeTests () =
         Assert.IsTrue(M5Interaction.resolveAction blockedWorld Outside |> Option.isNone)
 
     [<TestMethod>]
+    member _.TargetSelectionUsesPureDistancePriorityWithIdTiebreak () =
+        let doorPixel : PixelPosition =
+            { X = float32 (31 * Sim.tilePixels + Sim.tilePixels / 2)
+              Y = float32 (23 * Sim.tilePixels + Sim.tilePixels / 2) }
+        let avatar : Vec2 = { X = doorPixel.X - 32.0f; Y = doorPixel.Y }
+        let world = Sim.initialWorldN 42UL 2
+
+        // Door nearer than the villager: door wins by pure distance (no kind privilege).
+        let doorNearer =
+            { world with
+                Avatar = { world.Avatar with Pos = avatar }
+                Npcs = [| { world.Npcs.[0] with Pos = { X = avatar.X + 40.0f; Y = avatar.Y } } |] }
+        Assert.AreEqual<InteractionAction option>(Some(EnterHome(HomeId 1)), InteractionResolver.resolve doorNearer Outside |> Option.map (fun candidate -> candidate.Action))
+
+        // NPC nearer than the door: villager wins.
+        let npcNearerWorld = { doorNearer with Npcs = [| { world.Npcs.[0] with Pos = { X = avatar.X + 4.0f; Y = avatar.Y } } |] }
+        Assert.AreEqual<InteractionAction option>(Some(TalkTo(NpcId 0)), InteractionResolver.resolve npcNearerWorld Outside |> Option.map (fun candidate -> candidate.Action))
+
+        // Exact distance tie between two villagers: lower entity id wins deterministically.
+        let tieAvatar : Vec2 = { X = 1600.0f; Y = 800.0f }
+        let tieWorld =
+            { world with
+                Avatar = { world.Avatar with Pos = tieAvatar }
+                Npcs = [| { world.Npcs.[0] with Pos = { X = tieAvatar.X + 64.0f; Y = tieAvatar.Y } }
+                          { world.Npcs.[1] with Pos = { X = tieAvatar.X - 64.0f; Y = tieAvatar.Y } } |] }
+        Assert.AreEqual<InteractionAction option>(Some(TalkTo(NpcId 0)), InteractionResolver.resolve tieWorld Outside |> Option.map (fun candidate -> candidate.Action))
+
+        // Array snapshot immutability: neither resolve nor refreshPrompt may mutate Npcs.
+        let snapshot = Array.copy tieWorld.Npcs
+        let resolvedIgnore = InteractionResolver.resolve tieWorld Outside
+        CollectionAssert.AreEqual(snapshot, tieWorld.Npcs)
+        let view = M5Interaction.refreshPrompt tieWorld M5Interaction.initial
+        CollectionAssert.AreEqual(snapshot, tieWorld.Npcs)
+
+    [<TestMethod>]
     member _.WorldPanelDoesNotRenderA永久KeyList () =
         let world = Sim.initialWorldN 42UL 0
         let lines = M5Interaction.panelLines world M5Interaction.initial