refactor(runtime): consolidate followup, gateway, and provider dedupe paths

src/slack/monitor/message-handler/dispatch.ts

@@ -292,17 +292,7 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
         hasStreamedMessage = false;
       }
 
-      const replyThreadTs = replyPlan.nextThreadTs();
-      await deliverReplies({
-        replies: [payload],
-        target: prepared.replyTarget,
-        token: ctx.botToken,
-        accountId: account.accountId,
-        runtime,
-        textLimit: ctx.textLimit,
-        replyThreadTs,
-      });
-      replyPlan.markSent();
+      await deliverNormally(payload);
     },
     onError: (err, info) => {
       runtime.error?.(danger(`slack ${info.kind} reply failed: ${String(err)}`));
@@ -362,6 +352,18 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
     draftStream.update(trimmed);
     hasStreamedMessage = true;
   };
+  const onDraftBoundary =
+    useStreaming || !previewStreamingEnabled
+      ? undefined
+      : async () => {
+          if (hasStreamedMessage) {
+            draftStream.forceNewMessage();
+            hasStreamedMessage = false;
+            appendRenderedText = "";
+            appendSourceText = "";
+            statusUpdateCount = 0;
+          }
+        };
 
   const { queuedFinal, counts } = await dispatchInboundMessage({
     ctx: prepared.ctxPayload,
@@ -384,32 +386,8 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
           : async (payload) => {
               updateDraftFromPartial(payload.text);
             },
-      onAssistantMessageStart: useStreaming
-        ? undefined
-        : !previewStreamingEnabled
-          ? undefined
-          : async () => {
-              if (hasStreamedMessage) {
-                draftStream.forceNewMessage();
-                hasStreamedMessage = false;
-                appendRenderedText = "";
-                appendSourceText = "";
-                statusUpdateCount = 0;
-              }
-            },
-      onReasoningEnd: useStreaming
-        ? undefined
-        : !previewStreamingEnabled
-          ? undefined
-          : async () => {
-              if (hasStreamedMessage) {
-                draftStream.forceNewMessage();
-                hasStreamedMessage = false;
-                appendRenderedText = "";
-                appendSourceText = "";
-                statusUpdateCount = 0;
-              }
-            },
+      onAssistantMessageStart: onDraftBoundary,
+      onReasoningEnd: onDraftBoundary,
     },
   });
   await draftStream.flush();