test: replace /bin/sleep with portable Python sleep in test_gateway_init

/bin/sleep does not exist at FHS paths on NixOS (the KVM self-hosted
runner's OS). All 13 FileNotFoundError failures in TestSupervisor were
caused by _DaemonSpec tuples spawning /bin/sleep directly. Replace with
a module-level _SLEEP_30/_SLEEP_60 tuple using sys.executable so the
supervisor tests run on any platform. Also fix TestMainEndToEnd._run()
and remove the now-unnecessary setUpClass guard.

tests/unit/test_gateway_init.py

@@ -2,9 +2,8 @@
 
 Tests both the helper functions in `bot_bottle.gateway_init`
 and the supervisor's end-to-end signal / exit-code behavior. The
-end-to-end tests use real subprocesses (`/bin/sleep`,
+end-to-end tests use real subprocesses — short-lived, no docker required
-`/bin/sh -c '...'`) — short-lived, no docker required — so they
+— so they run under `tests/unit/` rather than `tests/integration/`."""
-run under `tests/unit/` rather than `tests/integration/`."""
 
 from __future__ import annotations
 
@@ -15,7 +14,6 @@ import sys
 import time
 import unittest
 import warnings
-from pathlib import Path
 from unittest.mock import patch
 
 from bot_bottle.gateway_init import (
@@ -26,6 +24,11 @@ from bot_bottle.gateway_init import (
     _selected_daemons,
 )
 
+# /bin/sleep does not exist on FHS-free systems (e.g. NixOS). Use a
+# portable Python one-liner so supervisor tests run on any platform.
+_SLEEP_30 = (sys.executable, "-c", "import time; time.sleep(30)")
+_SLEEP_60 = (sys.executable, "-c", "import time; time.sleep(60)")
+
 
 class TestEnvForDaemon(unittest.TestCase):
     """Scope egress-only credential env vars to the egress daemon.
@@ -182,7 +185,7 @@ class TestSupervisor(unittest.TestCase):
         # up and the supervisor never set shutdown_at.
         specs = [
             _DaemonSpec("crasher", ("/bin/sh", "-c", "exit 1")),
-            _DaemonSpec("longrun", ("/bin/sleep", "30")),
+            _DaemonSpec("longrun", _SLEEP_30),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -214,7 +217,7 @@ class TestSupervisor(unittest.TestCase):
         # signal-killed longrun's negative returncode.
         specs = [
             _DaemonSpec("crasher", ("/bin/sh", "-c", "exit 1")),
-            _DaemonSpec("longrun", ("/bin/sleep", "30")),
+            _DaemonSpec("longrun", _SLEEP_30),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -259,7 +262,7 @@ class TestSupervisor(unittest.TestCase):
         )
         specs = [
             _DaemonSpec("egress", sighup_marker),
-            _DaemonSpec("other",  ("/bin/sleep", "30")),
+            _DaemonSpec("other",  _SLEEP_30),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -282,7 +285,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_forward_signal_unknown_daemon_no_op(self):
-        specs = [_DaemonSpec("a", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("a", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         delivered = sup.forward_signal(signal.SIGHUP, "ghost")
@@ -294,8 +297,8 @@ class TestSupervisor(unittest.TestCase):
         # Restart one daemon; the other (supervise, the MCP server
         # in production) must remain untouched.
         specs = [
-            _DaemonSpec("git-gate", ("/bin/sleep", "30")),
+            _DaemonSpec("git-gate", _SLEEP_30),
-            _DaemonSpec("supervise", ("/bin/sleep", "30")),
+            _DaemonSpec("supervise", _SLEEP_30),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -319,8 +322,8 @@ class TestSupervisor(unittest.TestCase):
 
     def test_request_restart_is_drained_by_tick(self):
         specs = [
-            _DaemonSpec("git-gate", ("/bin/sleep", "30")),
+            _DaemonSpec("git-gate", _SLEEP_30),
-            _DaemonSpec("supervise", ("/bin/sleep", "30")),
+            _DaemonSpec("supervise", _SLEEP_30),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -343,7 +346,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_repeated_restart_requests_coalesce(self):
-        specs = [_DaemonSpec("git-gate", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("git-gate", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         time.sleep(0.1)
@@ -366,7 +369,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_request_restart_unknown_daemon_no_op(self):
-        specs = [_DaemonSpec("a", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("a", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         ok = sup.request_restart("ghost")
@@ -376,7 +379,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_restart_unknown_daemon_no_op(self):
-        specs = [_DaemonSpec("a", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("a", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         ok = sup.restart_daemon("ghost")
@@ -385,7 +388,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_restart_during_shutdown_is_no_op(self):
-        specs = [_DaemonSpec("git-gate", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("git-gate", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         sup.request_shutdown(reason="test")
@@ -395,7 +398,7 @@ class TestSupervisor(unittest.TestCase):
         self._drive(sup)
 
     def test_pending_restart_dropped_during_shutdown(self):
-        specs = [_DaemonSpec("git-gate", ("/bin/sleep", "30"))]
+        specs = [_DaemonSpec("git-gate", _SLEEP_30)]
         sup = _Supervisor(specs)
         sup.start_all()
         time.sleep(0.1)
@@ -413,8 +416,8 @@ class TestSupervisor(unittest.TestCase):
         # both should receive SIGTERM and exit. Signal-only
         # shutdown clamps to a zero supervisor exit code.
         specs = [
-            _DaemonSpec("a", ("/bin/sleep", "60")),
+            _DaemonSpec("a", _SLEEP_60),
-            _DaemonSpec("b", ("/bin/sleep", "60")),
+            _DaemonSpec("b", _SLEEP_60),
         ]
         sup = _Supervisor(specs)
         sup.start_all()
@@ -449,7 +452,7 @@ class TestSupervisor(unittest.TestCase):
         self.assertEqual(0, rc)
 
     def test_idempotent_shutdown_requests(self):
-        specs = [_DaemonSpec("a", ("/bin/sleep", "60"))]
+        specs = [_DaemonSpec("a", _SLEEP_60)]
         sup = _Supervisor(specs)
         sup.start_all()
         time.sleep(0.1)
@@ -465,28 +468,22 @@ class TestSupervisor(unittest.TestCase):
 
 class TestMainEndToEnd(unittest.TestCase):
     """Run gateway_init.py as a real subprocess to cover the
-    signal-handler installation path. Skipped on platforms
+    signal-handler installation path."""
-    without /bin/sleep + /bin/sh."""
-
-    @classmethod
-    def setUpClass(cls):
-        for p in ("/bin/sh", "/bin/sleep"):
-            if not Path(p).exists():
-                raise unittest.SkipTest(f"missing {p}")
 
     def _run(self, daemons_csv: str, send_signal: int | None,
              wait_before_signal: float = 0.4,
              overall_timeout: float = 6.0) -> tuple[int, str]:
         """Spawn gateway_init.main() in a child process with the
-        DAEMONS list patched to harmless `sleep 30` commands.
+        DAEMONS list patched to harmless long-sleep commands.
         Returns (returncode, captured stdout)."""
 
         helper = (
             "import os, runpy, sys\n"
             "from bot_bottle import gateway_init as si\n"
+            "sleep_cmd = (sys.executable, '-c', 'import time; time.sleep(30)')\n"
             "si._DAEMONS = (\n"
-            "  si._DaemonSpec('alpha', ('/bin/sleep','30')),\n"
+            "  si._DaemonSpec('alpha', sleep_cmd),\n"
-            "  si._DaemonSpec('beta',  ('/bin/sleep','30')),\n"
+            "  si._DaemonSpec('beta',  sleep_cmd),\n"
             ")\n"
             "sys.exit(si.main([]))\n"
         )