feat(discord): add autoArchiveDuration config option (#35065)

* feat(discord): add autoArchiveDuration config option

Add config option to control auto-archive duration for auto-created threads:

- autoArchiveDuration: 60 (default), 1440, 4320, or 10080
  - Sets archive duration in minutes (1hr/1day/3days/1week)
  - Accepts both string and numeric values
  - Discord's default was 60 minutes (hardcoded)

Example config:
```yaml
channels:
  discord:
    guilds:
      GUILD_ID:
        channels:
          CHANNEL_ID:
            autoThread: true
            autoArchiveDuration: 10080  # 1 week
```

* feat(discord): add autoArchiveDuration changelog entry (#35065) (thanks @davidguttman)

---------

Co-authored-by: Onur <onur@textcortex.com>

src/config/zod-schema.providers-core.ts

@@ -384,6 +384,16 @@ export const DiscordGuildChannelSchema = z
     systemPrompt: z.string().optional(),
     includeThreadStarter: z.boolean().optional(),
     autoThread: z.boolean().optional(),
+    /** Archive duration for auto-created threads in minutes. Discord supports 60, 1440 (1 day), 4320 (3 days), 10080 (1 week). Default: 60. */
+    autoArchiveDuration: z
+      .union([
+        z.enum(["60", "1440", "4320", "10080"]),
+        z.literal(60),
+        z.literal(1440),
+        z.literal(4320),
+        z.literal(10080),
+      ])
+      .optional(),
   })
   .strict();