fix(ai-moderation): bedah delay attachment ~330s -> target <20s

Root cause (trace msg 1541417073245290638):
- Race-guard upload-pending balik results:[] diperlakukan sbg SUKSES
  -> row yatam 'processing' sampai cleanup 300s mengembalikan
- Vision gagal 3x utk GIF besar (SSE truncation) tanpa fallback

Fix:
- Sinyal eksplisit uploadPending dari worker race guard
- Classifier murni classifyIndividualWorkerResult(): upload_pending ->
  requeue pending + reschedule segera (250ms), bukan error palsu;
  empty-results ok:true kini error transien (bug silent-success mati)
- llmVision fallback stream:false sekali saat SSE truncation
- Safety-net cleanup stuck processing 300s -> 120s

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

@@ -0,0 +1,65 @@
+/**
+ * fallbackResultClassifier.ts
+ *
+ * Pure classifier for the individual-fallback worker response.
+ *
+ * Bug history (2026-08-24): the worker's upload-pending race guard returned
+ * `{ ok: true, results: [] }` (a legacy "no results yet" signal), but the
+ * processor treated ANY `ok:true` as a successful moderation. Empty results
+ * meant nothing was written to the DB — the message stayed stuck in
+ * `ai_status='processing'` with nobody watching it until the 300s cleanup
+ * reverted it. That single gap produced the ~330-400s attachment delay
+ * cluster. Classification now happens in ONE pure function so every outcome
+ * has an explicit, testable owner.
+ */
+
+export type WorkerResultKind =
+  | "success"
+  | "upload_pending"
+  | "incomplete"
+  | "error";
+
+export interface ClassifiableWorkerResult {
+  ok?: boolean;
+  /** Upload-pending marker set by ai-analysis-worker's race guard. */
+  uploadPending?: boolean;
+  results?: Array<{ status?: string; flags?: string[] | string } | undefined>;
+  error?: string;
+}
+
+function flagsOf(r: { flags?: string[] | string }): string[] {
+  if (!r.flags) return [];
+  if (Array.isArray(r.flags)) return r.flags;
+  try {
+    const parsed = JSON.parse(r.flags) as unknown;
+    return Array.isArray(parsed) ? (parsed as string[]) : [];
+  } catch {
+    return [];
+  }
+}
+
+/**
+ * Classify an individual-fallback worker response:
+ * - "upload_pending": explicit race-guard signal — retry shortly, NOT an error.
+ * - "success": at least one result and none is analysis_incomplete.
+ * - "incomplete": LLM ran but dropped/failed this message after retries
+ *   (analysis_incomplete flag) — terminal exhausted path.
+ * - "error": anything else (ok:false, or ok:true with NO explainable
+ *   results). The old code silently succeeded here — never again.
+ */
+export function classifyIndividualWorkerResult(
+  result: ClassifiableWorkerResult,
+): WorkerResultKind {
+  if (result.uploadPending === true) return "upload_pending";
+  const results = (result.results ?? []).filter(
+    (r): r is NonNullable<typeof r> => Boolean(r),
+  );
+  if (results.length === 0) return "error";
+  if (result.ok !== true) return "error";
+  for (const r of results) {
+    const flags = flagsOf(r);
+    if (flags.includes("analysis_incomplete")) return "incomplete";
+    if ((r.status ?? "") === "") return "error";
+  }
+  return "success";
+}