chore(marketplace): add karpathy-guidelines-plugin, update dev-coding/dev-review/review-checklist

Karpathy 四原则融合到 req 技能工作流 (REQ-20260421-0003):
- dev-coding: 新增 Step 0「验证优先」(Goal-Driven Execution)
- dev-review: 五视角 → 六视角，新增 Scope 审计者 (Simplicity + Surgical)
- review-checklist/general: 新增 Karpathy 反模式速查表
- karpathy-guidelines-plugin: 新增独立插件，含四原则全文 + 与 req 工作流映射

.claude-plugin/marketplace.json

@@ -338,6 +338,18 @@
       ],
       "strict": false
     },
+    {
+      "name": "karpathy-guidelines-plugin",
+      "source": "./skills-dev/karpathy-guidelines-plugin",
+      "description": "Karpathy 四原则编码行为守则（Think Before Coding / Simplicity First / Surgical Changes / Goal-Driven Execution）。已深度融合到 req 技能工作流各阶段，可独立激活用于任意编码场景。",
+      "version": "1.0.0",
+      "category": "utility",
+      "keywords": [
+        "utility",
+        "tools"
+      ],
+      "strict": false
+    },
     {
       "name": "pull-request-plugin",
       "source": "./skills-dev/pull-request-plugin",