tmux_cmd(feat[logging]): Add structured extra to pre-execution log

why: Conform to CLAUDE.md logging standards — structured extra enables
assertion on record attributes instead of fragile string matching.
what:
- Add import shlex to common.py
- Replace subprocess.list2cmdline with shlex.join (POSIX quoting)
- Add extra={"tmux_cmd": ...} to pre-execution debug log
- Update test to assert on caplog.records attributes

Author: tony

src/libtmux/common.py

@@ -9,6 +9,7 @@
 
 import logging
 import re
+import shlex
 import shutil
 import subprocess
 import sys
@@ -259,7 +260,11 @@ def __init__(self, *args: t.Any, tmux_bin: str | None = None) -> None:
 
         self.cmd = cmd
 
-        logger.debug("running %s", subprocess.list2cmdline(cmd))
+        logger.debug(
+            "running %s",
+            shlex.join(cmd),
+            extra={"tmux_cmd": shlex.join(cmd)},
+        )
 
         try:
             self.process = subprocess.Popen(

tests/test_common.py

@@ -519,6 +519,6 @@ def test_tmux_cmd_pre_execution_logging(
     """Verify tmux_cmd logs command before execution."""
     with caplog.at_level(logging.DEBUG, logger="libtmux.common"):
         server.cmd("list-sessions")
-    assert any(
-        "running" in r.message and "list-sessions" in r.message for r in caplog.records
-    )
+    running_records = [r for r in caplog.records if hasattr(r, "tmux_cmd")]
+    assert len(running_records) > 0
+    assert "list-sessions" in running_records[0].tmux_cmd