feat: add self-update and improve skill selector

tests/test_create_workflow.py

@@ -1,11 +1,15 @@
 from __future__ import annotations
 
+import argparse
 import os
 import subprocess
 import sys
 import tempfile
 import unittest
 from pathlib import Path
+from unittest.mock import patch
+
+from skiff import cli
 
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
@@ -76,6 +80,19 @@ class CreateWorkflowTests(unittest.TestCase):
         self.assertIn("claude", first.stdout)
         self.assertIn("codex", first.stdout)
 
+    def test_update_pulls_skills_home(self) -> None:
+        with (
+            patch.object(cli, "SKILLS_HOME", self.skills_home),
+            patch.object(cli, "ensure_skills_home"),
+            patch.object(cli.subprocess, "run") as run,
+        ):
+            cli.cmd_update(argparse.Namespace())
+
+        run.assert_called_once_with(
+            ["git", "-C", str(self.skills_home), "pull"],
+            check=True,
+        )
+
     def test_create_writes_draft_and_brief_without_registering_owned_skill(self) -> None:
         project = self.home / "project"
         project.mkdir()