mcp(fix[pane]): Filter run_command sync line by UUID only

why: joining wrapped capture rows (tmux -J, as search and wait already
do) keeps the private sync line one logical row carrying the full
per-call channel and status option, so the over-broad substring markers
are unnecessary and only caused silent false drops of real output.
what:
- Capture with join_wrapped=True
- Match only the per-call channel and status option
- Drop the xfail and assert the sync line is dropped

Author: tony

src/libtmux_mcp/tools/pane_tools/io.py

@@ -204,7 +204,10 @@ async def run_command(
         with contextlib.suppress(Exception):
             pane.cmd("set-option", "-p", "-u", status_option)
 
-    raw_lines = await asyncio.to_thread(pane.capture_pane)
+    # join_wrapped keeps the private sync line a single logical row, so
+    # _filter_run_command_internal_lines can match it by the per-call
+    # channel/status option even when a wide prompt wraps it.
+    raw_lines = await asyncio.to_thread(pane.capture_pane, join_wrapped=True)
     visible_lines = _filter_run_command_internal_lines(
         raw_lines,
         channel=channel,
@@ -271,16 +274,14 @@ def _truncate_lines_tail(
 def _filter_run_command_internal_lines(
     lines: list[str], channel: str, status_option: str
 ) -> list[str]:
-    """Drop private synchronisation commands from captured command output."""
-    internal_markers = (
-        channel,
-        status_option,
-        "__libtmux_mcp_status",
-        "libtmux_mcp_",
-        "mcp_status",
-        "tmux wait-for -S",
-        "tmux set-option -p",
-    )
+    """Drop the private synchronisation line from captured output.
+
+    Matches only the per-call ``channel`` and ``status_option`` (random
+    hex that never collides with real output). ``run_command`` captures
+    with ``join_wrapped`` so the line stays one logical row even under a
+    wide prompt, keeping both markers intact.
+    """
+    internal_markers = (channel, status_option)
     return [
         line for line in lines if not any(marker in line for marker in internal_markers)
     ]

tests/test_pane_tools.py

@@ -245,10 +245,6 @@ class FilterInternalLinesFixture(t.NamedTuple):
 ]
 
 
-@pytest.mark.xfail(
-    strict=True,
-    reason="#76: over-broad markers drop legitimate run_command output",
-)
 @pytest.mark.parametrize(
     FilterInternalLinesFixture._fields,
     FILTER_KEEP_FIXTURES,
@@ -269,6 +265,23 @@ def test_filter_run_command_keeps_legitimate_output(test_id: str, line: str) ->
     assert kept == [line]
 
 
+def test_filter_run_command_drops_sync_line() -> None:
+    """The joined private synchronisation line is removed from output."""
+    from libtmux_mcp.tools.pane_tools.io import _filter_run_command_internal_lines
+
+    command_id = "deadbeefdeadbeefdeadbeefdeadbeef"
+    channel = f"libtmux_mcp_run_{command_id}"
+    status_option = f"@libtmux_mcp_status_{command_id}"
+    sync_line = (
+        f"}}; __libtmux_mcp_status=$?; tmux set-option -p {status_option} "
+        f'"$__libtmux_mcp_status"; tmux wait-for -S {channel}'
+    )
+    kept = _filter_run_command_internal_lines(
+        ["RUN_OK", sync_line], channel=channel, status_option=status_option
+    )
+    assert kept == ["RUN_OK"]
+
+
 def test_capture_pane(mcp_server: Server, mcp_pane: Pane) -> None:
     """capture_pane returns pane content."""
     result = capture_pane(