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/git_gate.py

@@ -15,9 +15,9 @@ a bare repo on the gate; `git daemon` serves the bare repos over
 
 The agent never sees the upstream credential under either path.
 
-Why a third sidecar (not folded into pipelock or ssh-gate): the
+Why a separate sidecar (not folded into egress or ssh-gate): the
 gate is the only one of the three that holds upstream push
-credentials. Mixing it with pipelock would put push creds in the
+credentials. Mixing it with egress would put push creds in the
 same blast radius as internet-facing TLS interception; mixing it
 with ssh-gate would force ssh-gate above L4 and into git-protocol
 land. See `docs/prds/0008-git-gate.md`.