chore(store): genericize email examples in docstring + test

Per CLAUDE.md vendor-agnostic OSS guidance — replace the real
groupon.com email used as a sanitize_username() example with a
placeholder (alice_smith@example.com).

src/store_naming.py

@@ -30,7 +30,7 @@ def sanitize_username(email: str) -> str:
     replaces every run of non-``[a-z0-9-]`` characters with a single ``-``,
     collapses repeats, and trims leading/trailing dashes.
 
-        sanitize_username("c_marustamyan@groupon.com")    -> "c-marustamyan"
+        sanitize_username("alice_smith@example.com")      -> "alice-smith"
         sanitize_username("john.doe+claude@acme.com")     -> "john-doe-claude"
         sanitize_username("USER@example.com")             -> "user"
 

tests/test_store_naming.py

@@ -15,7 +15,7 @@ from src.store_naming import (
 
 class TestSanitizeUsername:
     @pytest.mark.parametrize("email,expected", [
-        ("c_marustamyan@groupon.com", "c-marustamyan"),
+        ("alice_smith@example.com", "alice-smith"),
         ("john.doe+claude@acme.com", "john-doe-claude"),
         ("USER@example.com", "user"),
         ("a.b.c@x.y", "a-b-c"),