fixes for mksh tmux

mksh/mkshrc

@@ -1,5 +1,5 @@
-export HISTFILESIZE=10000
-export HISTCONTROL=ignoredups
+export HISTSIZE=10000          # mksh uses HISTSIZE; HISTFILESIZE is bash-only
+export HISTCONTROL=ignoredups  # bash-only, mksh ignores it (kept for other shells)
 export HISTFILE=$HOME/.cache/mksh_history
 export PAGER="less"
 export FCEDIT=nvim
@@ -11,7 +11,10 @@ ulimit -c unlimited
 stty -ixon
 bind '^l'=clear-screen
 bind '^k'=kill-line
-bind '^j'=kill-to-eol
+# Do NOT bind ^J: it is LF, i.e. the newline the line editor needs to submit a
+# command. Rebinding it makes Enter silently do nothing whenever the terminal
+# sends LF instead of CR (tmux extended-keys/CSI-u, pasted input, scripts) and
+# the shell looks hung. kill-to-eol is unbound now; ^U still does kill-line.
 bind '^e'=edit-line
 
 # alias dot='/usr/bin/git --work-tree=$DOTS --git-dir=$DOTS/.git'