refactor: rename teacher_ to master_ in all SKILL.md frontmatter, update descriptions

tools/cross_reference.py

@@ -305,7 +305,7 @@ def cmd_concept(bridge: FojinBridge, concept: str, teacher_slugs: list[str]) ->
 
 def main():
     parser = argparse.ArgumentParser(
-        description="Cross-reference Buddhist teachers and concepts via FoJin KG",
+        description="Cross-reference Buddhist masters and concepts via FoJin KG",
         formatter_class=argparse.RawDescriptionHelpFormatter,
         epilog="""Examples:
   %(prog)s lineage "印光" "蕅益"

tools/skill_writer.py

@@ -1,6 +1,6 @@
 """
 Skill Writer — creates and updates teacher skill directories.
-Adapted from colleague-skill's skill_writer.py for Buddhist teacher context.
+Adapted from colleague-skill's skill_writer.py for Buddhist master context.
 """
 
 import json
@@ -17,7 +17,7 @@ except ImportError:
 
 
 SKILL_MD_TEMPLATE = """---
-name: teacher_{slug}
+name: master_{slug}
 description: 依据{name}（{tradition}{school}）的教学风格与教义体系
 user-invocable: true
 ---