fix(hook): suppress peer list when daemon is unreachable

Fold daemonError into SessionAnnounceOptions so the helper owns the
mutually-exclusive choice between peer list and daemon-down hint. Before
this fix, a session-announce against an unreachable daemon emitted both
"No other mailboxes seen within the last 60 minutes (0 total registered)."
(misleading — the daemon was never asked) AND the daemon-unreachable hint.
Now only the hint appears when the daemon is down.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

node/src/cli.ts

@@ -260,8 +260,8 @@ program
       windowMinutes: opts.peerWindowMinutes,
       maxPeers: opts.maxPeers,
       watcherCommand: `claude-mailbox watch --block --name ${name}`,
+      daemonError: daemonError ?? undefined,
     });
-    if (daemonError) lines.push("", daemonError);
     lines.push("");
     process.stdout.write(lines.join("\n"));
   });