tmux_cmd(fix[logging]): guard pre-execution log with isEnabledFor

why: shlex.join(cmd) was computed unconditionally outside the
isEnabledFor guard, wasting cycles when DEBUG is disabled.
what:
- Move cmd_str = shlex.join(cmd) inside the if logger.isEnabledFor block
- Matches the post-execution logging pattern at line 307

Author: tony

src/libtmux/common.py

@@ -260,12 +260,13 @@ def __init__(self, *args: t.Any, tmux_bin: str | None = None) -> None:
 
         self.cmd = cmd
 
-        cmd_str = shlex.join(cmd)
-        logger.debug(
-            "running %s",
-            cmd_str,
-            extra={"tmux_cmd": cmd_str},
-        )
+        if logger.isEnabledFor(logging.DEBUG):
+            cmd_str = shlex.join(cmd)
+            logger.debug(
+                "running %s",
+                cmd_str,
+                extra={"tmux_cmd": cmd_str},
+            )
 
         try:
             self.process = subprocess.Popen(