Fix quick_validate UTF-8 decoding crash on Windows

read_text() uses the locale default encoding, which is cp1252 on Windows;
reading a UTF-8 SKILL.md (e.g. the claude-api skill, which contains emoji)
raised UnicodeDecodeError and crashed the validator. Read explicitly as
UTF-8, per the spec.

skills/skill-creator/scripts/quick_validate.py

@@ -19,7 +19,9 @@ def validate_skill(skill_path):
         return False, "SKILL.md not found"
 
     # Read and validate frontmatter
-    content = skill_md.read_text()
+    # Explicit UTF-8: read_text() uses the locale default encoding, which is
+    # cp1252 on Windows and crashes on UTF-8 SKILL.md files (e.g. emoji).
+    content = skill_md.read_text(encoding='utf-8')
     if not content.startswith('---'):
         return False, "No YAML frontmatter found"