`auto` and `pythonic` serializer aliases are not canonicalized → cache-miss on every read

[27Bslash6]

Summary

auto and pythonic both map to AutoSerializer, but only std/standard → default is canonicalized in the serializer-name guard. An entry written with serializer='pythonic' stores 's':'pythonic' in the CK frame; a handler configured serializer='auto' hits the mismatch guard and raises → treated as a miss → recompute on every read.

Evidence

• src/cachekit/serializers/__init__.py:54-55 — both alias to AutoSerializer
• src/cachekit/cache_handler.py:329 canonicalizes only std/standard→default; mismatch guard at :669-675

Impact

Two advertised aliases for the identical serializer silently break cache compatibility.

Fix

Canonicalize pythonic → auto (and any other aliases) before the name-equality guard.