Added Mystery Box Support

Added the event specific Mystery Box support to the exporter. Closes #7

docs/export-format.md

@@ -15,7 +15,7 @@ decoder-only offsets.
   "capture_source": "npcap",
   "exporter": {
     "name": "nte-history-exporter",
-    "version": "0.1.10"
+    "version": "0.1.11"
   },
   "banner": {
     "id": "Lottery_Permanent",
@@ -71,6 +71,8 @@ Current stable pool IDs:
 - `Lottery_LimitedCharacter`: Limited Character Board. New limited character
   banners should still use this ID while they share the same history/pity pool.
 - `Arc_MiracleBox`: Arc Miracle Box.
+- `Gashapon_MysteryBox`: Mystery Box. Records are single pulls and history is
+  not split into event rotations by the exporter.
 
 Avoid using `banner.name`, `reward_name`, `reward_type` or `reward_rank` as primary IDs. They
 are useful display fields, but may change when mapping files are updated.
@@ -110,6 +112,9 @@ Arc source:
 nte|gashapon|pool_group_id|timestamp_raw|timestamp_group_ordinal
 ```
 
+Mystery Box uses the same Gashapon UID source. Reward quantity is preserved,
+but each record represents exactly one pull and has `result_type = single_pull`.
+
 ## Example records
 
 Monopoly:
@@ -146,6 +151,24 @@ Arc:
 }
 ```
 
+Mystery Box:
+
+```json
+{
+  "uid": "2610c6e96afd64aa4a53fb9e8cebe031",
+  "pool_group_id": "Gashapon_MysteryBox",
+  "timestamp": "2026-07-08 19:09:33",
+  "timestamp_group_ordinal": 0,
+  "result_type": "single_pull",
+  "reward_type": "item",
+  "reward_id": "vehicle039",
+  "reward_name": "Draco",
+  "reward_rank": "S",
+  "quantity": 1,
+  "source_type": "mystery_box"
+}
+```
+
 ## CSV diagnostics
 
 CSV exports are mainly for debugging the decoder. Tools should prefer JSON