feat: add skill draft workflow

skiff/paths.py

@@ -8,6 +8,7 @@ HOME = Path.home()
 SKILLS_HOME = HOME / ".skills"
 SKILLS_DIR = SKILLS_HOME / "skills"
 TEMPLATE_DIR = SKILLS_DIR / "_template"
+DRAFTS_DIR = SKILLS_HOME / ".drafts"
 REGISTRY_FILE = SKILLS_HOME / "registry.yaml"
 EXTERNALS_DIR = HOME / ".local" / "share" / "skills" / "externals"
 PROJECT_MANIFEST = ".skills.yaml"
@@ -44,5 +45,5 @@ def agent_skill_dir(target: str, *, project_root: Path | None = None) -> Path:
 def ensure_skills_home() -> None:
     if not SKILLS_HOME.is_dir():
         raise SystemExit(
-            f"~/.skills 未配置。请先运行: skiff setup <skills-repo-path>"
+            "~/.skills 不存在。请将 skills 仓库克隆到 ~/.skills"
         )