Fix duplicate mod error with Space Age DLC mods (#576)

Skip downloading built-in DLC mods (elevated-rails, quality, space-age) when UPDATE_MODS_ON_START is enabled. These mods are included with the Space Age DLC and attempting to download them separately causes "Duplicate mod" errors.

- Modified update-mods.sh to skip DLC built-in mods during updates
- Added documentation note explaining the automatic handling of DLC mods

🤖 Generated with [Claude Code](https://claude.ai/code)

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

README.md

@@ -6,9 +6,9 @@
 [中文](./README_zh_CN.md)
 
 <!-- start autogeneration tags -->
-* `latest, 2.0.60`
+* `latest, 2.0.59`
 * `2, 2.0, 2.0.55, stable, stable-2.0.55`
-* `2.0.59`
+* `2.0.58`
 * `stable-1.1.110, 1, 1.1, 1.1.110`
 * `1.0.0, 1.0`
 * `0.17.79, 0.17`

buildinfo.json

@@ -362,14 +362,8 @@
   "2.0.59": {
     "sha256": "fdc467bf80e3611d6dd08c79492228ffec53f3fe914f24d793cac254d9353ff7",
     "tags": [
+      "latest",
       "2.0.59"
     ]
-  },
-  "2.0.60": {
-    "sha256": "69b5be1a867fd99524f9914dfee900a1ac386cf4e74c4a63768c05dc4d2b2b0b",
-    "tags": [
-      "latest",
-      "2.0.60"
-    ]
   }
 }