feat(macos): spike rootless Docker inside bottles

Add an opt-in docker_access path that layers rootless Docker tooling onto the selected agent image, starts the daemon only after registration, and retains the existing outer network and capability boundary. Include fail-closed bootstrap checks plus a live-Mac Compose/security acceptance test.\n\nRefs #392.

bot_bottle/backend/macos_container/launch.py

@@ -64,6 +64,7 @@ from .gateway_hosts import (
     refresh_gateway_host,
     set_gateway_host,
 )
+from . import rootless_docker
 from .bottle_plan import MacosContainerBottlePlan
 from ...orchestrator.config_store import resolve_teardown_timeout
 from .consolidated_launch import (
@@ -171,6 +172,10 @@ def launch(
         # token above, so — unlike the run-time env — the plan CAN carry it.
         plan = dataclasses.replace(plan, identity_token=ctx.identity_token)
 
+        exec_env = {
+            **_identity_proxy_env(endpoint, ctx.identity_token),
+            **rootless_docker.guest_env(plan.docker_access),
+        }
         bottle = MacosContainerBottle(
             plan.container_name,
             teardown,
@@ -184,10 +189,13 @@ def launch(
             ),
             terminal_color=plan.spec.color,
             agent_workdir=plan.workspace_plan.workdir,
-            exec_env=_identity_proxy_env(endpoint, ctx.identity_token),
+            exec_env=exec_env,
         )
         bottle.prompt_path = provision(plan, bottle)
 
+        if plan.docker_access:
+            rootless_docker.start(bottle)
+
         yield bottle
     finally:
         teardown()
@@ -199,15 +207,22 @@ def _build_images(plan: MacosContainerBottlePlan) -> MacosContainerBottlePlan:
     committed = read_committed_image(plan.slug)
     if committed and container_mod.image_exists(committed):
         info(f"using committed image {committed!r}")
-        return dataclasses.replace(
+        plan = dataclasses.replace(
             plan,
             agent_provision=dataclasses.replace(
                 plan.agent_provision, image=committed,
             ),
         )
-    container_mod.build_image(
-        plan.image, _REPO_DIR, dockerfile=plan.dockerfile_path,
-    )
+    else:
+        container_mod.build_image(
+            plan.image, _REPO_DIR, dockerfile=plan.dockerfile_path,
+        )
+    if plan.docker_access:
+        image = rootless_docker.build_image(plan.image, container_mod.build_image)
+        plan = dataclasses.replace(
+            plan,
+            agent_provision=dataclasses.replace(plan.agent_provision, image=image),
+        )
     return plan