fix: smoke-test agent images after build, add start --no-cache

npm treats optionalDependencies failures as non-fatal, so a transient
network blip fetching claude-code's platform-native binary during
`npm install -g` left a stub CLI in an image that still "built"
successfully — then got baked into the Docker/Container layer cache
until forced to rebuild. Post-build smoke test (provider-declared
argv, run in a throwaway container of the freshly built image) fails
the launch loudly instead of shipping a broken image; --no-cache
gives an escape hatch to force a from-scratch rebuild.

Closes #353.

bot_bottle/backend/docker/launch.py

@@ -36,6 +36,7 @@ from contextlib import ExitStack, contextmanager
 from pathlib import Path
 from typing import Callable, Generator
 
+from ...agent_provider import runtime_for
 from ...egress import egress_resolve_token_values
 from ...git_gate import (
     provision_git_gate_dynamic_keys,
@@ -111,6 +112,9 @@ def launch(
                 plan.image, _REPO_DIR,
                 dockerfile=plan.dockerfile_path,
             )
+            docker_mod.verify_agent_image(
+                plan.image, runtime_for(plan.agent_provider_template).smoke_test,
+            )
 
         internal_network = network_mod.network_name_for_slug(plan.slug)
         egress_network = network_mod.network_egress_name_for_slug(plan.slug)