refactor: send cmd verbatim, drop /bin/sh -c wrap

commands.run / stream now forward the user-supplied command string as
`cmd` instead of repackaging it as `cmd=/bin/sh args=["-c", cmd]`.
Callers that want shell semantics or argv splitting handle it
themselves; stream still accepts an optional `args` list for explicit
argv. Updated docstrings and payload tests accordingly.

tests/test_git.py

@@ -988,14 +988,14 @@ class TestAsyncGit:
         assert len(branches) == 2
 
 
-# ════════════════════════════════<EFBFBD><EFBFBD>═════════════════════════════════
-# Command payload tests — verify /bin/sh -c wrapping
-# ════════════════════════════<EFBFBD><EFBFBD><EFBFBD>══════════════════════<EFBFBD><EFBFBD><EFBFBD>══════════════
+# ══════════════════════════════════════════════════════════════════
+# Command payload tests — verify cmd passed verbatim, no sh -c wrap
+# ══════════════════════════════════════════════════════════════════
 
 
 class TestCommandPayloadWrapping:
-    """Verify that Commands.run sends cmd=/bin/sh args=['-c', cmd_string]
-    so the server-side wrapper expands "${@}" into proper argv."""
+    """Verify that Commands.run sends the full command string as ``cmd``
+    with no auto ``/bin/sh -c`` wrapping or args splitting."""
 
     @respx.mock
     def test_simple_command(self):
@@ -1005,15 +1005,13 @@ class TestCommandPayloadWrapping:
         git = _make_git()
         git.init("/repo")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", git_cmd_from_body(body)]
-        # args[1] should contain the actual git command
-        assert body["args"][0] == "-c"
-        assert "git" in body["args"][1]
+        assert "args" not in body
+        assert "git" in body["cmd"]
+        assert "init" in body["cmd"]
 
     @respx.mock
     def test_command_with_pipes(self):
-        """Pipes and redirects work because /bin/sh interprets them."""
+        """Shell metacharacters are forwarded verbatim — caller owns shell semantics."""
         from wrenn.client import WrennClient
         from wrenn.commands import Commands
 
@@ -1023,8 +1021,8 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response(stdout="3\n"))
         commands.run("cat /etc/passwd | wc -l")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "cat /etc/passwd | wc -l"]
+        assert body["cmd"] == "cat /etc/passwd | wc -l"
+        assert "args" not in body
 
     @respx.mock
     def test_command_with_semicolons(self):
@@ -1037,8 +1035,8 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         commands.run("cd /tmp; ls -la && echo done")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "cd /tmp; ls -la && echo done"]
+        assert body["cmd"] == "cd /tmp; ls -la && echo done"
+        assert "args" not in body
 
     @respx.mock
     def test_command_with_env_vars(self):
@@ -1051,8 +1049,8 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         commands.run("FOO=bar echo $FOO")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "FOO=bar echo $FOO"]
+        assert body["cmd"] == "FOO=bar echo $FOO"
+        assert "args" not in body
 
     @respx.mock
     def test_command_with_subshell(self):
@@ -1065,8 +1063,8 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         commands.run("echo $(date +%s)")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "echo $(date +%s)"]
+        assert body["cmd"] == "echo $(date +%s)"
+        assert "args" not in body
 
     @respx.mock
     def test_command_with_quotes_and_spaces(self):
@@ -1079,10 +1077,8 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         commands.run("""echo "hello 'world'" | grep -o "'[^']*'" """)
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"][0] == "-c"
-        # The command string is passed verbatim — shell interprets it
-        assert "hello 'world'" in body["args"][1]
+        assert "args" not in body
+        assert "hello 'world'" in body["cmd"]
 
     @respx.mock
     def test_heredoc_style_command(self):
@@ -1095,20 +1091,18 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         commands.run("python3 -c 'import sys; print(sys.version)'")
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "python3 -c 'import sys; print(sys.version)'"]
+        assert body["cmd"] == "python3 -c 'import sys; print(sys.version)'"
+        assert "args" not in body
 
     @respx.mock
     def test_git_shlex_joined_command(self):
-        """Git module uses shlex.join — verify it passes through correctly."""
+        """Git module uses shlex.join — verify it passes through as cmd."""
         route = respx.post(EXEC_URL).respond(200, json=_exec_response())
         git = _make_git()
         git.clone("https://github.com/user/repo.git", "/tmp/repo", depth=1)
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"][0] == "-c"
-        # shlex.join produces: git clone --depth 1 https://... /tmp/repo
-        shell_cmd = body["args"][1]
+        assert "args" not in body
+        shell_cmd = body["cmd"]
         assert "git" in shell_cmd
         assert "clone" in shell_cmd
         assert "--depth" in shell_cmd
@@ -1125,13 +1119,12 @@ class TestCommandPayloadWrapping:
         route = respx.post(EXEC_URL).respond(200, json={"pid": 42, "tag": "bg-1"})
         commands.run("tail -f /var/log/syslog", background=True)
         body = json.loads(route.calls[0].request.content)
-        assert body["cmd"] == "/bin/sh"
-        assert body["args"] == ["-c", "tail -f /var/log/syslog"]
+        assert body["cmd"] == "tail -f /var/log/syslog"
+        assert "args" not in body
         assert body["background"] is True
 
 
 def git_cmd_from_body(body: dict) -> str:
-    """Extract the shell command string from a wrapped payload."""
-    assert body["cmd"] == "/bin/sh"
-    assert body["args"][0] == "-c"
-    return body["args"][1]
+    """Extract the command string from the payload."""
+    assert "args" not in body
+    return body["cmd"]