refactor: master 沿用 release 轨道名，develop 用 develop，feature 用 feature

上一版把 master 的轨道也改名成 master，会把历史构建号搬到新键上。
改为 master/main 继续用现有的 release 轨（build_map 原地保留），
只有 develop 等其它上架分支新建以分支名命名的轨道并复制一份构建号。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BJaZ913U5GVdTkYHiRpvDU

config.example.json

@@ -74,10 +74,10 @@
   },
   "versions": {
     "tracks": {
-      "master": { "kind": "release", "app_ver": "2.180.0", "build_map": {} },
+      "release": { "kind": "release", "app_ver": "2.180.0", "build_map": {} },
       "develop": { "kind": "release", "app_ver": "2.180.0", "build_map": {} },
       "feature": { "kind": "feature", "app_ver": "2.180.0", "build_map": {} }
     }
   },
-  "branch_track": { "master": "master", "develop": "develop" }
+  "branch_track": { "master": "release", "develop": "develop" }
 }