feat(pouch): add skill structure audit to cut token waste

Teach pouch to optimize a named skill's loading layout: keep SKILL.md as a
router, move mode-specific steps to references, and measure footprint with
an audit script instead of dumping the whole skill into context.

tests/test_pouch_audit_skill_structure.py

@@ -0,0 +1,76 @@
+from __future__ import annotations
+
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+SCRIPT = (
+    REPO_ROOT
+    / "skills"
+    / "pouch"
+    / "scripts"
+    / "audit_skill_structure.py"
+)
+
+
+class AuditSkillStructureTests(unittest.TestCase):
+    def _write_skill(self, root: Path, *, body: str, description: str = "short") -> Path:
+        skill = root / "demo"
+        skill.mkdir()
+        (skill / "SKILL.md").write_text(
+            "---\n"
+            "name: demo\n"
+            f"description: {description}\n"
+            "---\n\n"
+            f"{body}\n",
+            encoding="utf-8",
+        )
+        return skill
+
+    def _run(self, skill_dir: Path) -> subprocess.CompletedProcess[str]:
+        return subprocess.run(
+            [sys.executable, str(SCRIPT), str(skill_dir)],
+            check=False,
+            capture_output=True,
+            text=True,
+        )
+
+    def test_reports_within_budget_and_reference_size(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            skill = self._write_skill(
+                Path(tmp),
+                body="# Demo\n\n## 步骤\n\n1. 做一件事。\n",
+            )
+            (skill / "references").mkdir()
+            (skill / "references" / "guide.md").write_text(
+                "# Guide\n\n细节。\n", encoding="utf-8"
+            )
+            result = self._run(skill)
+            self.assertEqual(result.returncode, 0, result.stderr)
+            self.assertIn("status: within-budget", result.stdout)
+            self.assertIn("## 步骤", result.stdout)
+            self.assertIn("references/guide.md", result.stdout)
+            self.assertIn("notes:", result.stdout)
+            self.assertIn("reference 未被 SKILL.md 链接: guide.md", result.stdout)
+
+    def test_flags_hard_budget_and_vague_references(self) -> None:
+        padding = "这是一段占位说明，用来把正文撑过硬顶。" * 400
+        with tempfile.TemporaryDirectory() as tmp:
+            skill = self._write_skill(
+                Path(tmp),
+                body="# Demo\n\n详见 references/。\n\n" + padding,
+            )
+            result = self._run(skill)
+            self.assertEqual(result.returncode, 0, result.stderr)
+            self.assertIn("status: over-hard-budget", result.stdout)
+            self.assertIn("HARD SKILL.md", result.stdout)
+            self.assertIn("见 references/", result.stdout)
+
+    def test_missing_skill_exits_2(self) -> None:
+        with tempfile.TemporaryDirectory() as tmp:
+            result = self._run(Path(tmp) / "missing")
+            self.assertEqual(result.returncode, 2)
+            self.assertIn("找不到 skill", result.stderr)