docs(cli): stereo pairing no longer requires a shared Marge account

The stereo pair guide still said pair creation requires both speakers to use
the same Marge account and backend. The account half stopped being true when
validateCreateCandidates dropped that check, which had rejected a real,
previously-working cross-account pair with no hardware or design requirement
behind it.

The backend requirement does still hold and is still enforced, so only the
account clause is corrected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/content/docs/guides/CLI-REFERENCE.md

@@ -861,9 +861,9 @@ Create and manage a persistent LEFT/RIGHT pair of two SoundTouch 10 speakers.
 This is distinct from a temporary multi-room zone. Both speakers must be
 online, stereo-capable, standalone, and outside any zone before a lifecycle
 operation. Pair creation also requires both speakers to use the same Marge
-account and backend. Run lifecycle commands from the site containing both
-speakers; site-relative Marge names such as `unifi` do not identify a remote
-site when resolved by the CLI host.
+backend, though they need not share a Marge account. Run lifecycle commands
+from the site containing both speakers; site-relative Marge names such as
+`unifi` do not identify a remote site when resolved by the CLI host.
 
 ```bash
 # Inspect a standalone speaker or either member of a pair