refactor(freezer): drop Bottle from commit signature

Freezer._freeze only ever used bottle.name, which is always
f"bot-bottle-{agent.slug}". Remove the Bottle parameter from
commit() and _freeze(), derive the container name from agent.slug
directly in each subclass, and delete the _NamedBottle stub that
existed solely to paper over this.

bot_bottle/backend/docker/freezer.py

@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from .. import ActiveAgent, Bottle
+from .. import ActiveAgent
 from ..freeze import Freezer
 from .util import commit_container
 from ...log import info
@@ -13,9 +13,10 @@ class DockerFreezer(Freezer):
 
     backend_name = "docker"
 
-    def _freeze(self, agent: ActiveAgent, bottle: Bottle) -> str:
+    def _freeze(self, agent: ActiveAgent) -> str:
+        container = f"bot-bottle-{agent.slug}"
         image_tag = f"bot-bottle-committed-{agent.slug}:latest"
-        commit_container(bottle.name, image_tag)
+        commit_container(container, image_tag)
         return image_tag
 
     def _export_hint(self, slug: str, image_ref: str) -> None: