fix(firecracker): make guest /tmp world-writable so agents can use it

The rootless agent rootfs build can land /tmp as 0755/root-owned, so the
agent (uid 1000 node) can't create scratch dirs there. The sandbox-escape
suite's README-push test does `cd /tmp && git init sandbox-escape-repo` and
died with "cannot mkdir sandbox-escape-repo: Permission denied" — before the
git-gate gitleaks hook could run — so the test read it as a missing hook.
On docker the agent inherits node:22-slim's 1777 /tmp, which is why only the
Firecracker path was affected (and only now that the suite runs end-to-end).

Set /tmp to 1777 in the guest PID-1 init, so every agent VM boots with a
usable /tmp regardless of rootfs perm drift.

Also update the infra-init unit test to assert the gateway launches via the
`bot_bottle.gateway_init` module (matching the prior fix), not a file path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A9qa3xoavjQScufDfZaXKR

bot_bottle/backend/firecracker/util.py

@@ -368,6 +368,11 @@ mount -t devtmpfs dev /dev 2>/dev/null
 mkdir -p /dev/pts && mount -t devpts devpts /dev/pts 2>/dev/null
 mount -o remount,rw / 2>/dev/null
 
+# /tmp must be world-writable + sticky. The rootless rootfs build can land
+# it 0755/root-owned, leaving the agent (uid 1000 node) unable to create
+# scratch dirs there — git worktrees, build temp, `git init /tmp/...`, etc.
+mkdir -p /tmp && chmod 1777 /tmp
+
 # Install the per-bottle SSH pubkey from the kernel cmdline.
 KEY=$(sed -n 's/.*bb_pubkey=\([^ ]*\).*/\1/p' /proc/cmdline | base64 -d 2>/dev/null)
 if [ -n "$KEY" ]; then

tests/unit/test_firecracker_infra_vm.py

@@ -38,7 +38,9 @@ class TestBuildInfraRootfs(unittest.TestCase):
         # and exports PATH so gateway_init's subprocess daemons find python3.
         init = build.call_args.kwargs["init_script"]
         self.assertIn("bot_bottle.orchestrator", init)
-        self.assertIn("gateway_init.py", init)
+        # Gateway launches via the installed package (there is no
+        # /app/gateway_init.py file since the daemons moved into bot_bottle).
+        self.assertIn("bot_bottle.gateway_init", init)
         self.assertIn("export PATH=", init)
         # Persistent registry volume mounted at the DB dir before the CP starts.
         self.assertIn("/dev/vdb", init)