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.ts

@@ -1,6 +1,25 @@
 export type PlayerStateName = "idle" | "playing" | "paused";
 export type OccupancyAction = "pause" | "resume" | "none";
 
+/**
+ * Convert a channel client-list length into the number of *other* users, or
+ * `null` when occupancy can't be determined.
+ *
+ * A connected bot is always a member of its own channel, so a valid query
+ * returns at least 1 (the bot itself). A length of 0 therefore does NOT mean
+ * "empty channel" — it means the underlying `clientlist` query failed (e.g. the
+ * full-client `clientlist` command times out when other clients are present,
+ * and `getClientsInChannel()` returns `[]` on error). Treating that failure as
+ * "empty" is what caused playback to auto-pause within seconds whenever a
+ * listener was actually in the channel. When the result is indeterminate we
+ * return `null` so callers skip the auto-pause/idle decision entirely rather
+ * than mis-reading an unknown state as empty.
+ */
+export function occupancyFromClientList(clientCount: number): number | null {
+  if (clientCount <= 0) return null; // query failed → occupancy unknown
+  return clientCount - 1; // exclude the bot itself
+}
+
 /**
  * Decide what auto-pause should do given channel occupancy.
  * - empty (userCount <= 0): pause iff enabled and currently playing.