fix(whatsapp): use conversation id for context isolation (#911)

Thanks @tristanmanchester.

Co-authored-by: Tristan Manchester <tmanchester96@gmail.com>

src/auto-reply/reply/agent-runner-utils.ts

@@ -25,13 +25,15 @@ export function buildThreadingToolContext(params: {
   if (!provider) return {};
   const dock = getChannelDock(provider);
   if (!dock?.threading?.buildToolContext) return {};
+  // WhatsApp context isolation keys off conversation id, not the bot's own number.
+  const threadingTo = provider === "whatsapp" ? sessionCtx.From ?? sessionCtx.To : sessionCtx.To;
   return (
     dock.threading.buildToolContext({
       cfg: config,
       accountId: sessionCtx.AccountId,
       context: {
         Channel: sessionCtx.Provider,
-        To: sessionCtx.To,
+        To: threadingTo,
         ReplyToId: sessionCtx.ReplyToId,
         ThreadLabel: sessionCtx.ThreadLabel,
       },