fix(reply): honour explicit [[reply_to_*]] tags when replyToMode is off

When replyToMode is 'off', explicit [[reply_to_current]] / [[reply_to:<id>]]
tags from the LLM were being stripped along with auto-injected reply threading.

Change the default for allowTagsWhenOff from false to true so explicit tags
are honoured on all channels, not just Slack. Channels can still opt out by
setting threading.allowTagsWhenOff to false in their dock definition.

Fixes #16155

src/auto-reply/reply/reply-threading.ts

@@ -54,9 +54,11 @@ export function createReplyToModeFilterForChannel(
   channel?: OriginatingChannelType,
 ) {
   const provider = normalizeChannelId(channel);
+  // Always honour explicit [[reply_to_*]] tags even when replyToMode is "off".
+  // Per-channel opt-out is possible but the safe default is to allow them.
   const allowTagsWhenOff = provider
-    ? Boolean(getChannelDock(provider)?.threading?.allowTagsWhenOff)
-    : false;
+    ? (getChannelDock(provider)?.threading?.allowTagsWhenOff ?? true)
+    : true;
   return createReplyToModeFilter(mode, {
     allowTagsWhenOff,
   });