fix: plugin bot user + await plugin detection before session scan

- Add EnsureBotUser on plugin activate (fixes 'Unable to find user' error)
- Accept bot_user_id in create session request
- Await plugin health check before starting session monitor
  (prevents race where sessions detect before plugin flag is set)
- Plugin now creates custom_livestatus posts with proper bot user

src/plugin-client.js

@@ -60,13 +60,24 @@ PluginClient.prototype.isHealthy = function () {
  * @param {string} agentId
  * @returns {Promise<string>} post_id
  */
+/**
+ * @param {string} botUserId - Mattermost bot user ID to author the post
+ */
+PluginClient.prototype.setBotUserId = function (botUserId) {
+  this.botUserId = botUserId;
+};
+
 PluginClient.prototype.createSession = function (sessionKey, channelId, rootId, agentId) {
-  return this._request('POST', '/api/v1/sessions', {
+  var body = {
     session_key: sessionKey,
     channel_id: channelId,
     root_id: rootId || '',
     agent_id: agentId,
-  }).then(function (data) {
+  };
+  if (this.botUserId) {
+    body.bot_user_id = this.botUserId;
+  }
+  return this._request('POST', '/api/v1/sessions', body).then(function (data) {
     return data.post_id;
   });
 };

src/watcher-manager.js

@@ -171,13 +171,17 @@ async function startDaemon() {
       logger: logger.child({ module: 'plugin-client' }),
     });
 
-    // Initial plugin detection
-    pluginClient.isHealthy().then(function (healthy) {
+    // Initial plugin detection (awaited before monitor starts — see below)
+    try {
+      var healthy = await pluginClient.isHealthy();
       usePlugin = healthy;
       logger.info({ usePlugin, url: config.plugin.url }, healthy
         ? 'Plugin detected — using WebSocket rendering mode'
         : 'Plugin not available — using REST API fallback');
-    });
+    } catch (_detectErr) {
+      usePlugin = false;
+      logger.warn('Plugin detection failed — using REST API fallback');
+    }
 
     // Periodic re-detection
     setInterval(function () {