chore: remove all pipelock references from tests, docs, and non-pipelock source

- Strip pipelock from all unit and integration test fixtures:
  proxy_plan fields removed from DockerBottlePlan/SmolmachinesBottlePlan
  constructors; pipelock-specific test classes deleted or renamed
- Update test_sidecar_init: remove test_pipelock_loses_egress_tokens,
  rename "pipelock" daemon fixtures to "git-gate" throughout
- Remove test_pipelock_binary_present_and_versioned from integration test
- Remove test_pipelock_answers_on_bundle_ip from smolmachines launch test
- Update _SANDBOX_BLOCK_MARKERS: remove "pipelock" marker (egress blocks)
- Dockerfile.sidecars: remove pipelock build stage and COPY; update layout
  comments and port table
- egress_entrypoint.sh: update comments now that egress is sole proxy
- Clean up pipelock references in comments/docstrings across backend,
  network, manifest, supervise, git_gate, yaml_subset, agent_provider,
  sidecar_bundle, sidecar_init, egress_addon_core modules

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bot_bottle/backend/smolmachines/local_registry.py

@@ -48,7 +48,7 @@ from ...log import die
 
 
 # registry:2.8.3, pinned by digest. Same env-override pattern as the
-# pipelock image pin in bot_bottle/backend/docker/pipelock.py.
+# sidecar image pin in bot_bottle/backend/docker/sidecar_bundle.py.
 REGISTRY_IMAGE = os.environ.get(
     "BOT_BOTTLE_REGISTRY_IMAGE",
     "registry@sha256:a3d8aaa63ed8681a604f1dea0aa03f100d5895b6a58ace528858a7b332415373",