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>

packages/shared/src/database/schema.ts

@@ -1,5 +1,6 @@
 import {
   bigint as pgBigint,
+  boolean as pgBoolean,
   foreignKey as pgForeignKey,
   index as pgIndex,
   integer as pgInteger,
@@ -30,6 +31,12 @@ export const pgMessagesTable = pgTable(
     type: pgText("type", { enum: ["text", "edited", "deleted"] })
       .notNull()
       .default("text"),
+    is_reply: pgBoolean("is_reply"),
+    is_forward: pgBoolean("is_forward"),
+    is_crosspost: pgBoolean("is_crosspost"),
+    reference_message_id: pgText("reference_message_id"),
+    reference_channel_id: pgText("reference_channel_id"),
+    reference_guild_id: pgText("reference_guild_id"),
     metadata: pgText("metadata"),
     ai_status: pgText("ai_status", {
       enum: ["pending", "processing", "clean", "warn", "flagged", "error"],

packages/shared/src/moderation-types.ts

@@ -64,6 +64,12 @@ export interface MessageRecord {
   edited_at: number | null;
   deleted_at: number | null;
   type: "text" | "edited" | "deleted";
+  is_reply: boolean | null;
+  is_forward: boolean | null;
+  is_crosspost: boolean | null;
+  reference_message_id: string | null;
+  reference_channel_id: string | null;
+  reference_guild_id: string | null;
   metadata: string | null;
   ai_status?: AIStatus | null;
   ai_moderation_flags?: string | null;