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/egress_entrypoint.sh

@@ -28,7 +28,7 @@ set -e
 # flag mitmdump would generate a fresh CA on the wrong path and
 # the agent's installed trust anchor would no longer match the
 # bumped leaf certs.
-CONFDIR=/home/mitmproxy/.mitmproxy
+CONFDIR="${EGRESS_CONFDIR:-/home/mitmproxy/.mitmproxy}"
 CONFDIR_FLAG="--set confdir=$CONFDIR"
 
 MODE="--mode regular@9099"