fix: party log --stop closes only the pipes it opened

Start already skipped panes the host had piped for other purposes,
but --stop swept every pane, killing pipes party log never owned.
Record the pane ids we pipe in .log-panes inside the per-party dir
and close exactly those on --stop; the file dies with the dir.

tests/87-log.bats

@@ -79,6 +79,16 @@ poll_for() {
   grep -q marker-KEEP "$saved"
 }
 
+@test "log --stop leaves a manually piped pane alone" {
+  "$PARTY_BIN" host bystander
+  manual="$PARTY_TMP/manual-pipe.out"
+  tmux -S "$(sock_of bystander)" pipe-pane -t bystander "cat >> '$manual'"
+  "$PARTY_BIN" log
+  "$PARTY_BIN" log --stop
+  tmux -S "$(sock_of bystander)" send-keys -t bystander 'echo marker-MANUAL' Enter
+  poll_for "$manual" marker-MANUAL
+}
+
 @test "close without a transcript stays silent about rescue" {
   export HOME="$PARTY_TMP/home"
   mkdir -p "$HOME"