fix(macos-container): make backend the macos default

bot_bottle/backend/__init__.py

@@ -24,9 +24,10 @@ backend exposes five methods:
       enough metadata for callers (CLI `list active`, dashboard
       agents pane) to render a row.
 
-Selection is driven by `--backend` on `start` or
-BOT_BOTTLE_BACKEND (env var; default "smolmachines"). Per PRD 0003 the
-manifest does not carry a backend field; the host picks.
+Selection is driven by `--backend` on `start` or BOT_BOTTLE_BACKEND
+(env var). When neither is set, compatible macOS hosts default to
+`macos-container`; other hosts default to `smolmachines`. Per PRD 0003
+the manifest does not carry a backend field; the host picks.
 """
 
 from __future__ import annotations
@@ -553,17 +554,24 @@ def get_bottle_backend(
     `name` precedence:
       1. explicit arg (CLI `--backend=<name>` passes through here)
       2. BOT_BOTTLE_BACKEND env var
-      3. default `smolmachines`
+      3. `macos-container` on compatible macOS hosts
+      4. default `smolmachines`
 
     Dies with a pointer at the known backends if the chosen name
     isn't implemented."""
-    resolved = name or os.environ.get("BOT_BOTTLE_BACKEND") or "smolmachines"
+    resolved = name or os.environ.get("BOT_BOTTLE_BACKEND") or _default_backend_name()
     if resolved not in _BACKENDS:
         known = ", ".join(sorted(_BACKENDS))
         die(f"unknown backend {resolved!r}; known backends: {known}")
     return _BACKENDS[resolved]
 
 
+def _default_backend_name() -> str:
+    if has_backend("macos-container"):
+        return "macos-container"
+    return "smolmachines"
+
+
 def known_backend_names() -> tuple[str, ...]:
     """Sorted tuple of all backend keys in `_BACKENDS`. Used by
     argparse (`--backend` choices) and the dashboard's backend

bot_bottle/backend/macos_container/backend.py

@@ -25,7 +25,7 @@ from .bottle_plan import MacosContainerBottlePlan
 class MacosContainerBottleBackend(
     BottleBackend["MacosContainerBottlePlan", "MacosContainerBottleCleanupPlan"]
 ):
-    """Experimental Apple Container backend. Selected by
+    """Apple Container backend. Selected by
     `BOT_BOTTLE_BACKEND=macos-container` or
     `--backend=macos-container`."""
 

bot_bottle/backend/macos_container/launch.py

@@ -36,7 +36,7 @@ from .bottle_plan import MacosContainerBottlePlan
 
 
 _REPO_DIR = str(Path(__file__).resolve().parent.parent.parent.parent)
-_SIDECAR_SLEEP_SECONDS = "2147483647"
+_AGENT_SLEEP_SECONDS = "2147483647"
 
 
 def internal_network_name(slug: str) -> str:
@@ -259,7 +259,7 @@ def _agent_run_argv(
     ]
     for entry in _agent_env_entries(plan, sidecar_ip):
         argv += ["--env", entry]
-    argv += [plan.image, "sleep", _SIDECAR_SLEEP_SECONDS]
+    argv += [plan.image, "sleep", _AGENT_SLEEP_SECONDS]
     return argv