feat: detect reply/forward/crosspost in message capture + inject into AI moderation

- Add is_reply, is_forward, is_crosspost, reference_message_id,
  reference_channel_id, reference_guild_id columns to messages table
- Update MessageRecord type with reference fields
- Extract reply/forward/crosspost from Discord message type/flags
- Track reference.type (DEFAULT=reply, FORWARD) and CROSSPOSTED flag
- Inject <reference> XML with parent content into LLM moderation prompt
- Add reply/forward/crosspost rules to moderation prompt rules
- Format context messages with [reply_to], [forward_from], [crosspost]
- Add migration 0009

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

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

@@ -40,6 +40,26 @@ export function estimateTokens(text: string): number {
   return tokens;
 }
 
+/**
+ * Formats reference info for a message (reply/forward/crosspost)
+ */
+function formatReferenceInfo(msg: MessageRecord): string {
+  const parts: string[] = [];
+  if (msg.is_reply && msg.reference_message_id) {
+    parts.push(`[reply_to: ${msg.reference_message_id}]`);
+    if (msg.reference_channel_id) {
+      parts.push(`(reply_channel: ${msg.reference_channel_id})`);
+    }
+  }
+  if (msg.is_forward && msg.reference_message_id) {
+    parts.push(`[forward_from: ${msg.reference_message_id}]`);
+  }
+  if (msg.is_crosspost) {
+    parts.push(`[crosspost]`);
+  }
+  return parts.length > 0 ? ` ${parts.join(" ")}` : "";
+}
+
 /**
  * Formats a single message for context or target display
  */
@@ -51,7 +71,8 @@ export function formatMessageForPrompt(
   const timestamp = formatTimestamp(msg.created_at);
   const mediaEvidence = formatMediaEvidenceForPrompt(msg.metadata);
   const mediaSuffix = mediaEvidence ? ` ${mediaEvidence}` : "";
-  return `[${label}] id=${msg.id} time=${timestamp} user=${msg.username}: ${content}${mediaSuffix}`;
+  const refInfo = formatReferenceInfo(msg);
+  return `[${label}] id=${msg.id} time=${timestamp} user=${msg.username}: ${content}${mediaSuffix}${refInfo}`;
 }
 
 /**