refactor(slack): move Slack channel code to extensions/slack/src/ (#45621)

Move all Slack channel implementation files from src/slack/ to
extensions/slack/src/ and replace originals with shim re-exports.
This follows the extension migration pattern for channel plugins.

- Copy all .ts files to extensions/slack/src/ (preserving directory
  structure: monitor/, http/, monitor/events/, monitor/message-handler/)
- Transform import paths: external src/ imports use relative paths
  back to src/, internal slack imports stay relative within extension
- Replace all src/slack/ files with shim re-exports pointing to
  the extension copies
- Update tsconfig.plugin-sdk.dts.json rootDir from "src" to "." so
  the DTS build can follow shim chains into extensions/
- Update write-plugin-sdk-entry-dts.ts re-export path accordingly
- Preserve extensions/slack/index.ts, package.json, openclaw.plugin.json,
  src/channel.ts, src/runtime.ts, src/channel.test.ts (untouched)

extensions/slack/src/sent-thread-cache.ts

@@ -0,0 +1,79 @@
+import { resolveGlobalMap } from "../../../src/shared/global-singleton.js";
+
+/**
+ * In-memory cache of Slack threads the bot has participated in.
+ * Used to auto-respond in threads without requiring @mention after the first reply.
+ * Follows a similar TTL pattern to the MS Teams and Telegram sent-message caches.
+ */
+
+const TTL_MS = 24 * 60 * 60 * 1000; // 24 hours
+const MAX_ENTRIES = 5000;
+
+/**
+ * Keep Slack thread participation shared across bundled chunks so thread
+ * auto-reply gating does not diverge between prepare/dispatch call paths.
+ */
+const SLACK_THREAD_PARTICIPATION_KEY = Symbol.for("openclaw.slackThreadParticipation");
+
+const threadParticipation = resolveGlobalMap<string, number>(SLACK_THREAD_PARTICIPATION_KEY);
+
+function makeKey(accountId: string, channelId: string, threadTs: string): string {
+  return `${accountId}:${channelId}:${threadTs}`;
+}
+
+function evictExpired(): void {
+  const now = Date.now();
+  for (const [key, timestamp] of threadParticipation) {
+    if (now - timestamp > TTL_MS) {
+      threadParticipation.delete(key);
+    }
+  }
+}
+
+function evictOldest(): void {
+  const oldest = threadParticipation.keys().next().value;
+  if (oldest) {
+    threadParticipation.delete(oldest);
+  }
+}
+
+export function recordSlackThreadParticipation(
+  accountId: string,
+  channelId: string,
+  threadTs: string,
+): void {
+  if (!accountId || !channelId || !threadTs) {
+    return;
+  }
+  if (threadParticipation.size >= MAX_ENTRIES) {
+    evictExpired();
+  }
+  if (threadParticipation.size >= MAX_ENTRIES) {
+    evictOldest();
+  }
+  threadParticipation.set(makeKey(accountId, channelId, threadTs), Date.now());
+}
+
+export function hasSlackThreadParticipation(
+  accountId: string,
+  channelId: string,
+  threadTs: string,
+): boolean {
+  if (!accountId || !channelId || !threadTs) {
+    return false;
+  }
+  const key = makeKey(accountId, channelId, threadTs);
+  const timestamp = threadParticipation.get(key);
+  if (timestamp == null) {
+    return false;
+  }
+  if (Date.now() - timestamp > TTL_MS) {
+    threadParticipation.delete(key);
+    return false;
+  }
+  return true;
+}
+
+export function clearSlackThreadParticipationCache(): void {
+  threadParticipation.clear();
+}