l4d2host: LEFT4ME_STEAMCMD env var for steamcmd path

SteamInstaller defaults to steamcmd="steamcmd" (bare name), which relies
on PATH lookup. Deployments that don't have steamcmd on PATH — or where
steamcmd.sh's `cd "$(dirname "$0")"` breaks under PATH-symlink invocation
(observed with the Valve-shipped script) — can now pin an absolute path
via LEFT4ME_STEAMCMD. Default keeps bare-name lookup for dev/tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

l4d2host/cli.py

@@ -1,5 +1,6 @@
 from pathlib import Path
 import json
+import os
 import subprocess
 
 import typer
@@ -21,8 +22,13 @@ def _exit_from_subprocess_error(exc: subprocess.CalledProcessError) -> None:
 
 @app.command()
 def install() -> None:
+    # LEFT4ME_STEAMCMD lets deployment pin an absolute path (e.g. when the
+    # binary lives outside PATH or its steamcmd.sh resolves $0 via dirname,
+    # which breaks under PATH-symlink invocation). Default keeps PATH lookup
+    # for dev/tests.
+    steamcmd = os.environ.get("LEFT4ME_STEAMCMD", "steamcmd")
     try:
-        SteamInstaller().install_or_update(passthrough=True)
+        SteamInstaller(steamcmd=steamcmd).install_or_update(passthrough=True)
     except subprocess.CalledProcessError as exc:
         _exit_from_subprocess_error(exc)
 

l4d2host/tests/test_cli.py

@@ -14,6 +14,44 @@ def test_help_lists_v1_commands() -> None:
         assert command in result.output
 
 
+def test_install_uses_left4me_steamcmd_env_var(monkeypatch) -> None:
+    captured: dict[str, str] = {}
+
+    class FakeInstaller:
+        def __init__(self, *, steamcmd):
+            captured["steamcmd"] = steamcmd
+
+        def install_or_update(self, **kwargs):
+            del kwargs
+
+    monkeypatch.setattr("l4d2host.cli.SteamInstaller", FakeInstaller)
+    monkeypatch.setenv("LEFT4ME_STEAMCMD", "/opt/left4me/steam/steamcmd.sh")
+
+    result = CliRunner().invoke(app, ["install"])
+
+    assert result.exit_code == 0
+    assert captured["steamcmd"] == "/opt/left4me/steam/steamcmd.sh"
+
+
+def test_install_defaults_to_bare_steamcmd_when_env_unset(monkeypatch) -> None:
+    captured: dict[str, str] = {}
+
+    class FakeInstaller:
+        def __init__(self, *, steamcmd):
+            captured["steamcmd"] = steamcmd
+
+        def install_or_update(self, **kwargs):
+            del kwargs
+
+    monkeypatch.setattr("l4d2host.cli.SteamInstaller", FakeInstaller)
+    monkeypatch.delenv("LEFT4ME_STEAMCMD", raising=False)
+
+    result = CliRunner().invoke(app, ["install"])
+
+    assert result.exit_code == 0
+    assert captured["steamcmd"] == "steamcmd"
+
+
 def test_cli_propagates_subprocess_return_code(monkeypatch) -> None:
     def fail(*args, **kwargs):
         del args