chore(skill): 安全扫描警告清零 + 加入 skill-gate CI

- scan-skill.sh: loopback 不算风险、命中走允许清单
- 11 个文件的 /Users/<机器名> 绝对路径去环境化（脚本 $HOME、文档 ~）
- 允许清单登记运维环境地址与示例占位符（非凭据），附理由
- scan: 57 warns -> 0 warns / 0 high
- 新增 .gitea/workflows/skill-gate.yml（validate --strict + scan + catalog --check + 测试）

.gitea/workflows/skill-gate.yml

@@ -0,0 +1,30 @@
+name: skill-gate
+
+on:
+  pull_request:
+    paths:
+      - "skills-**"
+      - "scripts/**"
+      - "install-skills.sh"
+      - "catalog.json"
+  push:
+    branches: [main]
+    paths:
+      - "skills-**"
+      - "scripts/**"
+      - "install-skills.sh"
+      - "catalog.json"
+
+jobs:
+  gate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: 规范校验（strict：警告也算失败）
+        run: python3 scripts/validate-skills.py --strict
+      - name: 安全扫描（禁止高危项）
+        run: ./scripts/scan-skill.sh
+      - name: catalog 是否最新
+        run: python3 scripts/generate-catalog.py --check
+      - name: 安装器测试
+        run: bash tests/install-skills.test.sh