fix(auto-pause): never treat a failed clientlist as "channel empty"; default OFF

Auto-pause within the first seconds of playback (and re-pause after a manual
play) whenever a listener is actually in the channel.

Root cause (confirmed live against a TS3 server): the full-client
`clientlist -uid -away -voice -groups` command TIMES OUT when other clients are
present in the bot's channel. `getClientsInChannel()` catches the error and
returns `[]`, so the occupancy callers computed `userCount = [].length - 1 = -1`,
which `decideOccupancyAction` reads as `-1 <= 0` → "channel empty" → pause. With
the bot alone, clientlist succeeds (returns just the bot), so the bug only
surfaced when someone was listening — exactly the report.

Fix: a connected bot is always a member of its own channel, so a valid query
returns >= 1 (itself). A length of 0 therefore means the query FAILED, not that
the channel is empty. New pure helper `occupancyFromClientList()` maps a
0-length result to `null` ("occupancy unknown"); `refreshOccupancy()` and the
30s idle poller skip the auto-pause / idle-disconnect decision when the count is
unknown instead of mis-reading it as empty. This also removes a latent
false-positive idle-disconnect on the same failed query.

Also default `autoPauseOnEmpty` to OFF (occupancy detection is unreliable on
some servers); users can opt in from Settings.

Verified live with two clients in one channel: clientlist returns 0 → helper
returns null → no false pause (control: bot alone returns 1 → 0 others, normal).

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

src/bot/auto-pause.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "vitest";
-import { decideOccupancyAction } from "./auto-pause.js";
+import { decideOccupancyAction, occupancyFromClientList } from "./auto-pause.js";
 
 describe("decideOccupancyAction", () => {
   it("pauses when empty while playing and enabled", () => {
@@ -27,3 +27,21 @@ describe("decideOccupancyAction", () => {
     expect(decideOccupancyAction("paused", true, false, 1)).toBe("resume");
   });
 });
+
+describe("occupancyFromClientList", () => {
+  it("returns null when the query failed (0 clients — bot itself is always present)", () => {
+    // This is the bug fix: a clientlist timeout makes getClientsInChannel()
+    // return [], which must be treated as "unknown", NOT as an empty channel.
+    expect(occupancyFromClientList(0)).toBeNull();
+  });
+  it("returns 0 other users when only the bot is in the channel", () => {
+    expect(occupancyFromClientList(1)).toBe(0);
+  });
+  it("excludes the bot itself from the count", () => {
+    expect(occupancyFromClientList(2)).toBe(1);
+    expect(occupancyFromClientList(5)).toBe(4);
+  });
+  it("never yields a negative count (guards the -1 that caused false pauses)", () => {
+    expect(occupancyFromClientList(-3)).toBeNull();
+  });
+});