fix(sidecars): apply_routes_change targets the bundle + SIGHUP forwarding

Two bugs surfaced when applying an egress route change:

1. egress_apply.py still targeted claude-bottle-egress-<slug> —
   the legacy per-sidecar container that no longer exists (it's
   a docker-network alias on the bundle now). Switched it to
   sidecar_bundle_container_name(slug), matching the chunk-5
   fix already made to pipelock_apply.py.

2. `docker kill --signal HUP <bundle>` lands SIGHUP on the
   supervisor (PID 1 in the bundle), which previously had no
   SIGHUP handler — the signal was ignored. Added
   `_Supervisor.forward_signal(sig, daemon_name)` and a SIGHUP
   handler in main() that forwards to the egress daemon so
   mitmdump's addon reload still works under the bundle.

Tests:
- New _Supervisor.forward_signal cases: forwards to the named
  child (Python subprocess as the SIGHUP target — bash trap +
  stdout=PIPE deferral interferes with the production-style
  test); unknown-daemon name is a no-op.

Stale-reference cleanup (separate issue surfaced while looking
at this):
- claude_bottle/{egress,git_gate,egress_addon,
  egress_addon_core,supervise_server}.py: Dockerfile.egress /
  Dockerfile.git-gate / Dockerfile.supervise references updated
  to Dockerfile.sidecars (the old per-sidecar Dockerfiles were
  deleted in PRD 0024 chunk 5).
- tests/README.md: dropped the entry for
  test_pipelock_sidecar_smoke (deleted in chunk 3) and added
  the new bundle integration tests.
- git_gate.py: stale `DockerGitGate.start via docker cp`
  reference (the method was deleted in chunk 3) rewritten to
  the bind-mount path the renderer uses now.

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

tests/README.md

@@ -40,15 +40,17 @@ Discovery is invoked with `-t .` (top-level dir = repo root) so the
 
 ## What the integration tests cover
 
-- `test_pipelock_sidecar_smoke.py` — drives `DockerPipelockProxy.prepare`
-  + `.start` (the production code path) against a real Docker daemon and
-  probes the sidecar's `/health` from an in-network curl container.
 - `test_dry_run_plan.py` — `cli.py start --dry-run --format=json` emits
   a structured plan that contains the resolved egress allowlist and
   the bottle's runtime, and creates zero Docker resources.
-- `test_orphan_cleanup.py` — `network_remove` and `PipelockProxy.stop`
-  are idempotent against missing resources, so the EXIT trap can call
-  them unconditionally.
+- `test_orphan_cleanup.py` — `network_remove` is idempotent against
+  missing resources, so the EXIT trap can call it unconditionally.
+- `test_sidecar_bundle_image.py` — builds Dockerfile.sidecars and
+  probes that pipelock / gitleaks / mitmdump / supervise are all
+  reachable inside the bundle.
+- `test_sidecar_bundle_compose.py` — end-to-end compose-up of an
+  agent + bundle pair; verifies the agent reaches the bundle via
+  the legacy network aliases.
 
 ## Canaries