Update documentation and docstrings for semantic matching

- Update spec document to match actual implementation:
  - assert_join_compatibility only checks if expr1 is U (not expr2)
  - Error message includes .join(semantic_check=False) suggestion
  - Use create_lineage_table function name
- Add complete parameter documentation to all lineage.py functions

Author: claude

docs/src/design/semantic-matching-spec.md

@@ -306,7 +306,7 @@ def assert_join_compatibility(expr1, expr2):
 
     Raises DataJointError if non-homologous namesakes are detected.
     """
-    if isinstance(expr1, U) or isinstance(expr2, U):
+    if isinstance(expr1, U):
         return  # U is always compatible
 
     # Find namesake attributes (same name in both)
@@ -320,7 +320,8 @@ def assert_join_compatibility(expr1, expr2):
             raise DataJointError(
                 f"Cannot join on attribute `{name}`: "
                 f"different lineages ({lineage1} vs {lineage2}). "
-                f"Use .proj() to rename one of the attributes."
+                f"Use .proj() to rename one of the attributes or "
+                f".join(semantic_check=False) to force a natural join."
             )
 ```
 
@@ -415,7 +416,7 @@ For existing schemas without `~lineage` tables:
 ```python
 def migrate_schema_lineage(schema):
     """Populate ~lineage table for all tables in schema."""
-    create_lineage_table_if_not_exists(schema)
+    create_lineage_table(schema)
 
     for table in schema.list_tables():
         populate_lineage_from_dependencies(schema, table)
@@ -452,7 +453,7 @@ Union requires all namesake attributes to have matching lineage (enforced via `a
 ```
 DataJointError: Cannot join on attribute `id`: different lineages
 (university.student.id vs university.course.id).
-Use .proj() to rename one of the attributes.
+Use .proj() to rename one of the attributes or .join(semantic_check=False) to force a natural join.
 ```
 
 ### Deprecated `@` Operator

src/datajoint/lineage.py

@@ -20,7 +20,12 @@
 
 
 def create_lineage_table(connection, database):
-    """Create the ~lineage table if it doesn't exist."""
+    """
+    Create the ~lineage table if it doesn't exist.
+
+    :param connection: database connection
+    :param database: schema/database name
+    """
     connection.query(
         f"""
         CREATE TABLE IF NOT EXISTS `{database}`.`{LINEAGE_TABLE_NAME}` (
@@ -37,8 +42,11 @@ def get_lineage(connection, database, table_name, attribute_name):
     """
     Get lineage for an attribute from the ~lineage table.
 
-    Returns the lineage string if found, None otherwise (indicating no lineage
-    or attribute is a native secondary).
+    :param connection: database connection
+    :param database: schema/database name
+    :param table_name: name of the table
+    :param attribute_name: name of the attribute
+    :return: lineage string if found, None otherwise (no lineage or native secondary)
     """
     try:
         result = connection.query(
@@ -59,8 +67,10 @@ def get_all_lineages(connection, database, table_name):
     """
     Get all lineage entries for a table.
 
-    Returns a dict mapping attribute_name -> lineage.
-    Attributes not in the dict have no lineage (native secondary).
+    :param connection: database connection
+    :param database: schema/database name
+    :param table_name: name of the table
+    :return: dict mapping attribute_name -> lineage (attributes not in dict have no lineage)
     """
     try:
         result = connection.query(
@@ -77,7 +87,13 @@ def get_all_lineages(connection, database, table_name):
 
 
 def delete_lineage_entries(connection, database, table_name):
-    """Delete all lineage entries for a table."""
+    """
+    Delete all lineage entries for a table.
+
+    :param connection: database connection
+    :param database: schema/database name
+    :param table_name: name of the table
+    """
     try:
         connection.query(
             f"""
@@ -95,6 +111,8 @@ def insert_lineage_entries(connection, database, entries):
     """
     Insert lineage entries for a table.
 
+    :param connection: database connection
+    :param database: schema/database name
     :param entries: list of (table_name, attribute_name, lineage) tuples
     """
     if not entries: