ci: 加 paths-ignore + landing concurrency cancel (省 GH Actions minutes)

對應 leo 2026-05-16 Actions 配額用爆 → 全面瘦身 CI trigger。

deploy.yml (Workers):
  既有：worker-level git diff filter（只 deploy 改到的 worker）✅
  新增：workflow-level paths-ignore — doc-only commit 完全不啟動 workflow
        排除：**.md / AGENTS.md / .agents/** / docs/** / registry/examples/** /
              registry/skills/** / .gitignore / LICENSE
  之前每個 doc push 都觸發 discover job 吃 ~1 min。
  本輪 LI 開發 ~10 doc-only commit = 省 ~10 min

deploy-landing.yml (Pages):
  既有：paths filter ('landing/**') ✅
  新增：concurrency cancel-in-progress (原 false → true)
  landing build ~3 min 是大頭，連續 push 取消舊 build 省最多

.github/workflows/deploy-landing.yml

@@ -15,7 +15,8 @@ on:
 
 concurrency:
   group: deploy-landing-${{ github.ref }}
-  cancel-in-progress: false
+  # 連續 push landing 改動時，舊 build 自動 cancel（landing build ~3 min 是大頭，省 minutes 關鍵）
+  cancel-in-progress: true
 
 jobs:
   deploy: