refactor(sidecars): drop vestigial start/stop methods (PRD 0024 chunk 3)

Compose-up has owned per-container lifecycle since PRD 0018 ch3;
the .start() / .stop() methods on DockerPipelockProxy /
DockerEgress / DockerGitGate / DockerSupervise (and their
abstractmethod declarations in the four base ABCs) were already
documented as vestigial. With the bundle path in flight
(PRD 0024 ch2), they are truly dead — collapse to nothing.

Changes:
- Removed start/stop methods from the four DockerSidecar
  classes. Plan dataclasses, image/path constants,
  container-name helpers, and the .prepare() methods all stay
  (the renderer + apply path still need them).
- Removed the matching @abstractmethod declarations in the
  base ABCs so concrete subclasses don't have to stub them.
- launch.launch() and prepare.resolve_plan() no longer take
  proxy/git_gate/egress/supervise instance parameters. backend.py
  loses the four instance attributes it threaded through.
  prepare.resolve_plan() instantiates the four classes itself
  to call their .prepare() methods.
- Deleted four integration tests that only exercised the
  removed lifecycle: test_pipelock_sidecar_smoke,
  test_supervise_sidecar, test_git_gate_sidecar,
  test_git_gate_mirror.
- Dropped the .stop-idempotency case in test_orphan_cleanup;
  the network-cleanup cases stay (those test real production
  code).
- Marked test_pipelock_apply @skip pending chunk 4 — its
  bringup helper used .start; chunk 4 rewrites it with direct
  `docker run`.

Dockerfile deletion deferred to chunk 5 (when the bundle flag
default flips) — the legacy compose path still needs
Dockerfile.{egress,git-gate,supervise} until then.

Net: 708 lines removed, 80 added.

533 unit tests + 27 integration tests passing (5 skipped: the
chunk-4-pending case + existing GITEA_ACTIONS guards).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

claude_bottle/backend/docker/launch.py

@@ -63,14 +63,11 @@ from .compose import (
     compose_up,
     write_compose_file,
 )
-from .egress import DockerEgress, egress_tls_init
-from .git_gate import DockerGitGate
+from .egress import egress_tls_init
 from .pipelock import (
-    DockerPipelockProxy,
     pipelock_proxy_url,
     pipelock_tls_init,
 )
-from .supervise import DockerSupervise
 
 
 # Where the repo root lives, for `docker build` context. Computed once.
@@ -81,21 +78,10 @@ _REPO_DIR = str(Path(__file__).resolve().parent.parent.parent.parent)
 def launch(
     plan: DockerBottlePlan,
     *,
-    proxy: DockerPipelockProxy,
-    git_gate: DockerGitGate,
-    egress: DockerEgress,
-    supervise: DockerSupervise,
     provision: Callable[[DockerBottlePlan, str], str | None],
 ) -> Generator[DockerBottle, None, None]:
     """Build, launch, and provision a Docker bottle via compose.
-    Teardown on exit. The per-sidecar `proxy / git_gate / egress /
-    supervise` parameters are vestigial from the pre-compose flow —
-    kept for backwards-compat with backend.py's call site; the
-    `start()`/`stop()` methods on those classes are no longer
-    invoked (chunk 3 collapsed them into the compose service spec).
-    They'll be removed entirely in a follow-up cleanup."""
-    del proxy, git_gate, egress, supervise  # not invoked in compose flow
-
+    Teardown on exit."""
     stack = ExitStack()
 
     def teardown() -> None: