feat(firecracker): enumerate running bottles

bot_bottle/backend/firecracker/enumerate.py

@@ -1,14 +1,32 @@
 """Active-agent enumeration for the Firecracker backend.
 
-The backend is disabled during the companion-container removal (#385) — it can't
-launch bottles, so there are none to enumerate. Real enumeration returns
-with the backend's consolidated relaunch (#354).
+Running bottles are the Firecracker processes whose ``--config-file`` points
+at an existing per-bottle run directory. The same authoritative process scan
+protects cleanup from deleting live VMs; operational scan failures propagate
+as ``EnumerationError`` instead of masquerading as an empty host.
 """
 
 from __future__ import annotations
 
+from ...bottle_state import read_metadata
 from .. import ActiveAgent
+from .cleanup import live_run_dirs
 
 
 def enumerate_active() -> list[ActiveAgent]:
-    return []
+    out: list[ActiveAgent] = []
+    for run_dir in live_run_dirs():
+        slug = run_dir.name
+        metadata = read_metadata(slug)
+        out.append(ActiveAgent(
+            backend_name="firecracker",
+            slug=slug,
+            agent_name=metadata.agent_name if metadata else "?",
+            started_at=metadata.started_at if metadata else "",
+            # Firecracker uses the shared gateway, so there are no
+            # per-bottle gateway service containers to report.
+            services=(),
+            label=metadata.label if metadata else "",
+            color=metadata.color if metadata else "",
+        ))
+    return out