fix(auto-delete): prevent double-processing + improve error classification

Two bugs causing 23 spurious 'error' logs after successful deletions:

1. batchProcessor switch missing 'completed' case: partitionBatchOutcome
   returns 'completed' for successful messages, but the switch only handled
   'upload_pending' and 'api_failed'. Successful messages fell through to
   default → re-enqueued to individual fallback → re-analyzed → re-delete
   attempt → error (message already gone from Discord). Now explicitly
   skips 'completed' messages.

2. isAlreadyDeletedError only caught codes 10008/404. Discord also returns
   10003 (Unknown Channel) and 50001 (Missing Access) when a message or
   channel is gone. Added these codes plus text-based fallback matching
   'Unknown Message'/'Unknown Channel'.

Impact: eliminates ~23 redundant error logs per day + stops wasted LLM
calls re-analyzing already-processed messages.

services/discord-gateway/src/modules/ai-moderation/autoDeleteManager.ts

@@ -130,7 +130,24 @@ function getErrorCode(error: unknown): number | string | undefined {
 
 function isAlreadyDeletedError(error: unknown): boolean {
   const code = getErrorCode(error);
-  return code === 10008 || code === 404 || code === "10008" || code === "404";
+  // Discord REST error codes for "message not found":
+  //   10008 = Unknown Message, 10003 = Unknown Channel,
+  //   50001 = Missing Access (channel deleted/hidden), 404 = HTTP
+  if (
+    code === 10008 ||
+    code === 10003 ||
+    code === 50001 ||
+    code === 404 ||
+    code === "10008" ||
+    code === "10003" ||
+    code === "50001" ||
+    code === "404"
+  )
+    return true;
+  // Fallback: check the message text for the Discord "Unknown Message" string
+  const msg =
+    error instanceof Error ? error.message : typeof error === "string" ? error : "";
+  return msg.includes("Unknown Message") || msg.includes("Unknown Channel");
 }
 
 function hasChannelMessagesApi(channel: unknown): channel is {

services/discord-gateway/src/modules/ai-moderation/batchProcessor.ts

@@ -233,6 +233,10 @@ export async function processBatch(
           // conversation cooldown instead of an immediate individual retry.
           apiFailedMessages.push(msg);
           break;
+        case "completed":
+          // Successfully analyzed — already broadcast + auto-delete scheduled
+          // above. Do NOT re-enqueue for individual fallback.
+          break;
         default:
           // incomplete / parse_failed / unexplained drops stay retryable via
           // the individual fallback queue (same semantics as before).