feat: add self-update and improve skill selector

tests/test_registry_collections.py

@@ -7,6 +7,9 @@ import sys
 import tempfile
 import unittest
 from pathlib import Path
+from unittest.mock import patch
+
+from skiff.registry import external_checkout_path, registry_repo
 
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
@@ -79,6 +82,17 @@ class RegistryCollectionTests(unittest.TestCase):
             check=False,
         )
 
+    def test_registry_repo_expands_home_relative_local_path(self) -> None:
+        with patch.dict(os.environ, {"HOME": str(self.home)}):
+            self.assertEqual(
+                registry_repo({"repo": "~/.skills"}),
+                str(self.skills_home),
+            )
+            self.assertEqual(
+                external_checkout_path("skills", {"repo": "~/.skills"}),
+                self.skills_home.resolve(),
+            )
+
     def test_add_collection_installs_every_discovered_skill(self) -> None:
         result = self.run_skiff("add", "test-pack", "-g", "-a", "codex")