feat(scope): player store scopedBotId + resolveScopedBot helper

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

web/src/stores/player.ts

@@ -1,5 +1,6 @@
 import { defineStore } from 'pinia';
 import axios from 'axios';
+import { resolveScopedBot } from './scope.js';
 
 export interface Song {
   id: string;
@@ -50,6 +51,9 @@ export const usePlayerStore = defineStore('player', {
   state: () => ({
     bots: [] as BotStatus[],
     activeBotId: null as string | null,
+    /** When set, the UI is locked to a single bot (dedicated link, from ?bot).
+     * Source of truth is the URL — never persisted to localStorage. */
+    scopedBotId: null as string | null,
     /** Per-bot queues keyed by botId */
     queues: {} as Record<string, Song[]>,
     /** Per-bot timing state keyed by botId */
@@ -73,6 +77,10 @@ export const usePlayerStore = defineStore('player', {
     activeBot(): BotStatus | null {
       return this.bots.find((b) => b.id === this.activeBotId) ?? this.bots[0] ?? null;
     },
+    /** True when the UI is locked to a single bot via a dedicated link. */
+    isScoped(): boolean {
+      return this.scopedBotId !== null;
+    },
     currentSong(): Song | null {
       return this.activeBot?.currentSong ?? null;
     },
@@ -125,6 +133,8 @@ export const usePlayerStore = defineStore('player', {
     },
 
     setActiveBotId(id: string) {
+      // While scoped to a dedicated link, switching bots is blocked.
+      if (this.scopedBotId !== null && id !== this.scopedBotId) return;
       this.activeBotId = id;
       // Fetch queue for newly active bot if we don't have it yet
       if (!this.queues[id]) {
@@ -132,6 +142,32 @@ export const usePlayerStore = defineStore('player', {
       }
     },
 
+    /** Lock the UI to a single bot (dedicated link). Sets scope first so the
+     * setActiveBotId guard does not block the switch to the scoped bot. */
+    setScope(id: string) {
+      this.scopedBotId = id;
+      this.activeBotId = id;
+      // Lazily fetch this bot's queue, mirroring setActiveBotId.
+      if (!this.queues[id]) {
+        this.fetchQueue();
+      }
+    },
+
+    clearScope() {
+      this.scopedBotId = null;
+    },
+
+    /** Reconcile the scope with the desired id from the URL (?bot). A stale or
+     * forbidden id resolves to null and clears the scope rather than locking. */
+    applyScopeFromQuery(requestedId: string | null) {
+      const r = resolveScopedBot(requestedId, this.bots.map((b) => b.id));
+      if (r) {
+        this.setScope(r);
+      } else if (requestedId) {
+        this.clearScope();
+      }
+    },
+
     updateBotStatus(botId: string, status: BotStatus) {
       const prev = this.bots.find((b) => b.id === botId);
       const prevSongId = prev?.currentSong?.id;

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();
+  });
+});

web/src/stores/scope.ts

@@ -0,0 +1,10 @@
+/** Given the desired scoped id (from ?bot) and the known bot ids, decide the
+ * effective scope. Returns the id if it exists, else null (graceful clear:
+ * a stale/forbidden id never locks the UI). */
+export function resolveScopedBot(
+  requestedId: string | null | undefined,
+  knownBotIds: readonly string[],
+): string | null {
+  if (!requestedId) return null;
+  return knownBotIds.includes(requestedId) ? requestedId : null;
+}