Move .env into skills/ for easy install

- Added skills/_env_loader.py - shared env loader for all scripts
- Updated 17 scripts to use load_unified_env()
- Updated install-skills.sh to copy .env into skills/
- Updated README with simpler OpenClaw install instructions
- .env in skills/ is gitignored (credentials stay private)

skills/_env_loader.py

@@ -0,0 +1,14 @@
+import os
+from pathlib import Path
+from dotenv import load_dotenv
+
+
+def load_unified_env():
+    skills_root = Path(__file__).resolve().parent.parent
+    env_path = skills_root / ".env"
+    if env_path.exists():
+        load_dotenv(env_path)
+        return
+    legacy = Path.home() / ".config" / "opencode" / ".env"
+    if legacy.exists():
+        load_dotenv(legacy)