fix: remediate 10 review findings in communication spine

- Fix createSession race condition with in-flight promise map
- Fix listener leak: always cleanup previous subscription per client
- Fix REST timeout returning HTTP 200 — now rejects with 504
- Fix fire-and-forget Discord sends — await with error handling
- Fix non-null assertion on client.user in Discord plugin
- Fix TUI disconnect mid-stream deadlock (reset streaming state)
- Add connect_error handler to TUI and Discord plugin
- Add connected guard on TUI message submit
- Add relayEvent guard for disconnected sockets
- Sanitize error messages sent to WebSocket clients
- Add error logging/context to AgentService create/prompt/destroy

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/discord/src/index.ts

@@ -39,6 +39,15 @@ export class DiscordPlugin {
       console.log('[discord] Connected to gateway');
     });
 
+    this.socket.on('disconnect', (reason: string) => {
+      console.error(`[discord] Disconnected from gateway: ${reason}`);
+      this.pendingResponses.clear();
+    });
+
+    this.socket.on('connect_error', (err: Error) => {
+      console.error(`[discord] Gateway connection error: ${err.message}`);
+    });
+
     // Handle streaming text from gateway
     this.socket.on('agent:text', (data: { conversationId: string; text: string }) => {
       const pending = this.pendingResponses.get(data.conversationId);
@@ -51,8 +60,10 @@ export class DiscordPlugin {
     this.socket.on('agent:end', (data: { conversationId: string }) => {
       const text = this.pendingResponses.get(data.conversationId);
       if (text) {
-        this.sendToDiscord(data.conversationId, text);
         this.pendingResponses.delete(data.conversationId);
+        this.sendToDiscord(data.conversationId, text).catch((err) => {
+          console.error(`[discord] Error sending response for ${data.conversationId}:`, err);
+        });
       }
     });
 
@@ -79,18 +90,21 @@ export class DiscordPlugin {
     // Ignore bot messages
     if (message.author.bot) return;
 
+    // Not ready yet
+    if (!this.client.user) return;
+
     // Check guild binding
     if (this.config.guildId && message.guildId !== this.config.guildId) return;
 
     // Respond to DMs always, or mentions in channels
     const isDM = !message.guildId;
-    const isMention = message.mentions.has(this.client.user!);
+    const isMention = message.mentions.has(this.client.user);
 
     if (!isDM && !isMention) return;
 
     // Strip bot mention from message content
     const content = message.content
-      .replace(new RegExp(`<@!?${this.client.user!.id}>`, 'g'), '')
+      .replace(new RegExp(`<@!?${this.client.user.id}>`, 'g'), '')
       .trim();
 
     if (!content) return;
@@ -104,27 +118,45 @@ export class DiscordPlugin {
     }
 
     // Send to gateway
-    this.socket?.emit('message', {
+    if (!this.socket?.connected) {
+      console.error(
+        `[discord] Cannot forward message: not connected to gateway. channel=${channelId}`,
+      );
+      return;
+    }
+    this.socket.emit('message', {
       conversationId,
       content,
     });
   }
 
-  private sendToDiscord(conversationId: string, text: string): void {
+  private async sendToDiscord(conversationId: string, text: string): Promise<void> {
     // Find the Discord channel for this conversation
     const channelId = Array.from(this.channelConversations.entries()).find(
       ([, convId]) => convId === conversationId,
     )?.[0];
 
-    if (!channelId) return;
+    if (!channelId) {
+      console.error(`[discord] No channel found for conversation ${conversationId}`);
+      return;
+    }
 
     const channel = this.client.channels.cache.get(channelId);
-    if (!channel || !('send' in channel)) return;
+    if (!channel || !('send' in channel)) {
+      console.error(
+        `[discord] Channel ${channelId} not sendable for conversation ${conversationId}`,
+      );
+      return;
+    }
 
     // Chunk responses for Discord's 2000-char limit
     const chunks = this.chunkText(text, 1900);
     for (const chunk of chunks) {
-      (channel as { send: (content: string) => Promise<unknown> }).send(chunk);
+      try {
+        await (channel as { send: (content: string) => Promise<unknown> }).send(chunk);
+      } catch (err) {
+        console.error(`[discord] Failed to send message to channel ${channelId}:`, err);
+      }
     }
   }