fix(smolmachines): consolidate virtiofs mounts to stay within libkrun limit

libkrun limits total mounts + port-mappings to 5. With all three
sidecar daemons active (egress, git-gate, supervise), the prior
layout used 3 mounts + 3 ports = 6, causing the VM to crash at boot
with krun_start_enter returned -22.

Merge the egress confdir and git-gate scripts into a single staging
directory mounted at /bot-bottle-data/ with egress/ and git-gate/
subdirectories, reducing to 2 mounts + 3 ports = 5. Also clean up
leftover VMs before creating new ones to handle interrupted teardowns.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bot_bottle/backend/smolmachines/sidecar_bundle.py

@@ -135,6 +135,16 @@ def start_bundle_vm(
         elif entry in effective_host_env:
             env[entry] = effective_host_env[entry]
     name = bundle_machine_name(spec.slug)
+    # Destroy any leftover machine from a previous run that didn't
+    # clean up (e.g. crash, interrupted teardown).
+    try:
+        _smolvm.machine_stop(name)
+    except _smolvm.SmolvmError:
+        pass
+    try:
+        _smolvm.machine_delete(name)
+    except _smolvm.SmolvmError:
+        pass
     _smolvm.machine_create(
         name,
         from_path=from_path,