CLI and dashboard now share one cross-backend abstraction for
listing + launching bottles, so adding a backend (docker /
smolmachines) lights up in both places without separate wiring.

Backend abstraction:
- New `ActiveBottle` dataclass (`backend_name`, `slug`,
  `agent_name`, `started_at`, `services`) replaces the
  docker-specific `ActiveAgent`. Same field surface for the
  existing dashboard consumers; `ActiveAgent` becomes a typed
  alias for source-compat.
- New `BottleBackend.enumerate_active() -> Sequence[ActiveBottle]`
  replaces the old `list_active() -> None` (which printed and
  returned nothing). Docker implements it via the existing
  compose query; smolmachines implements it via `smolvm machine
  ls --json` cross-referenced with each bundle container's
  `CLAUDE_BOTTLE_SIDECAR_DAEMONS` env (`backend/smolmachines/
  enumerate.py`).
- New `enumerate_active_bottles()` and `known_backend_names()`
  module-level helpers fold every backend into one call.
- `get_bottle_backend(name=None)` takes an optional explicit
  name (precedence: arg > $CLAUDE_BOTTLE_BACKEND > "docker").

CLI:
- `./cli.py list active` enumerates every backend, prints
  tab-separated `<backend>\t<slug>\t<agent>\t<services>`. The
  smolmachines bottle the user was looking for now shows up.
- `./cli.py start` grows `--backend=<docker|smolmachines>`
  (choices pulled live from `known_backend_names()`). Threaded
  through `prepare_with_preflight(backend_name=...)` so the
  resume path picks up the flag too.

Dashboard:
- Active agents pane lists both backends (the row formatter now
  prefixes `[docker]` / `[smolmachines]`).
- New-agent flow inserts a backend picker modal between agent
  pick and preflight (`_backend_picker_modal`). Short-circuits
  when only one backend is registered.
- `discover_active_agents()` collapses to
  `enumerate_active_bottles()`; `_parse_services_by_project` and
  `_query_services_by_project` move to
  `backend/docker/cleanup.py` where the docker enumerator owns
  them.

Tests: parser + enumerate-active tests relocated to
`test_docker_enumerate_active.py`. New
`test_backend_selection.py` covers `get_bottle_backend`,
`known_backend_names`, `enumerate_active_bottles`. New
`test_cli_start_backend_flag.py` covers `--backend`'s argparse
shape + the explicit-over-env precedence.

605 unit tests pass.

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

@@ -178,0 +175,4 @@
+    nothing's running."""
+    # docker on PATH? Defensive — `list active` shouldn't die
+    # just because the docker backend isn't usable on this host.
+    if shutil.which("docker") is None:

@@ -175,3 +170,1 @@
-        ps = subprocess.run(
-            ["docker", "compose", "-p", project, "ps", "--format",
-             "{{.Service}}\t{{.Name}}\t{{.Status}}"],
+def enumerate_active() -> list[ActiveBottle]:

@@ -0,0 +70,4 @@
+    Smolmachines bundles all run the PRD-0024 image with the
+    same daemon set declared via env, so one inspect per bundle
+    gets us the picture without exec'ing into the container."""
+    if shutil.which("docker") is None:

@@ -109,0 +103,4 @@
+# Field surface stays compatible (slug / agent_name / started_at
+# / services) plus a new `backend_name` so dashboard rows can
+# show which backend a bottle came from.
+ActiveAgent = ActiveBottle

@@ -166,5 +166,5 @@
         except OSError as e:
             warn(f"failed to remove {path}: {e}")
 
 
 def enumerate_active() -> list[ActiveBottle]:

@@ -174,5 +174,5 @@
     consume this. Empty list when docker is unreachable or
     nothing's running."""
     # docker on PATH? Defensive — `list active` shouldn't die
     # just because the docker backend isn't usable on this host.
     if shutil.which("docker") is None:

@@ -0,0 +70,4 @@
+
+def _query_bundle_services() -> dict[str, tuple[str, ...]]:
+    """`{slug: ('egress', 'pipelock', ...)}` from each running
+    bundle container's `CLAUDE_BOTTLE_SIDECAR_DAEMONS` env var.

@@ -169,0 +103,4 @@
+    backend is reachable. Backed by the shared
+    `enumerate_active_agents` helper so the CLI's
+    `./cli.py list active` and this dashboard show the same data."""
+    return enumerate_active_agents()

@@ -184,1 +164,3 @@
-    print()
+# `enumerate_active` moved to `backend/docker/enumerate.py` to
+# mirror the smolmachines layout. Cleanup keeps the orphan
+# enumeration; enumeration of live agents is its own concern.

@@ -13,3 +3,1 @@
-The actual `docker ps` invocation is exercised by manual probing
-during development and the (real-docker) integration tests; here
-we lock down the shape contract so a regression surfaces in unit CI.
+The active-bottle enumeration tests moved to

@@ -0,0 +174,4 @@
+        )
+
+    # `noop when docker missing` lives at the cross-backend gate
+    # now (`enumerate_active_agents` skips backends whose

@@ -162,5 +162,5 @@
 
 
 # `enumerate_active` moved to `backend/docker/enumerate.py` to
 # mirror the smolmachines layout. Cleanup keeps the orphan
 # enumeration; enumeration of live agents is its own concern.

@@ -16,3 +1,3 @@
-"""
+"""Unit: dashboard's row-formatting + selection helpers (PRD 0019)."""
 
 from __future__ import annotations

@@ -0,0 +174,4 @@
+        )
+
+
+if __name__ == "__main__":