feat(scope): player store scopedBotId + resolveScopedBot helper

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/stores/scope.test.ts

@@ -0,0 +1,16 @@
+import { describe, it, expect } from "vitest";
+import { resolveScopedBot } from "./scope.js";
+
+describe("resolveScopedBot", () => {
+  it("returns null when no id requested", () => {
+    expect(resolveScopedBot(null, ["a", "b"])).toBeNull();
+    expect(resolveScopedBot(undefined, ["a"])).toBeNull();
+    expect(resolveScopedBot("", ["a"])).toBeNull();
+  });
+  it("returns the id when it exists in the bot list", () => {
+    expect(resolveScopedBot("b", ["a", "b"])).toBe("b");
+  });
+  it("clears (null) when the requested id is not a known bot", () => {
+    expect(resolveScopedBot("ghost", ["a", "b"])).toBeNull();
+  });
+});