fix(tmux): accept OSC 52 from panes so nested tmux copy reaches the clipboard

The local tmux left set-clipboard at the default "external", which drops
OSC 52 sent by applications in a pane. In a nested setup the remote tmux
sends its copies up as OSC 52, so they never reached the Mac clipboard.

.local/bin/pbcopy

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# pbcopy -- macOS-style clipboard copy for this headless box.
+#
+# There is no X/Wayland display here, so xclip/xsel cannot reach a clipboard.
+# Instead we use OSC 52: the text is handed to the terminal emulator on the
+# other end of the SSH connection, which puts it on YOUR machine's clipboard.
+#
+#   ls -la | pbcopy
+#   pbcopy < notes.md
+
+set -euo pipefail
+
+# A real local display (rare here, but free to support).
+if [[ -n "${DISPLAY:-}" ]] && command -v xclip >/dev/null 2>&1; then
+    exec xclip -selection clipboard
+fi
+if [[ -n "${WAYLAND_DISPLAY:-}" ]] && command -v wl-copy >/dev/null 2>&1; then
+    exec wl-copy
+fi
+
+# Inside tmux: load-buffer -w fills the tmux paste buffer and, because
+# set-clipboard is on, forwards OSC 52 out to the terminal emulator.
+if [[ -n "${TMUX:-}" ]] && command -v tmux >/dev/null 2>&1; then
+    exec tmux load-buffer -w -
+fi
+
+# Bare SSH: emit OSC 52 straight at the controlling terminal.
+{ printf '\033]52;c;'; base64 | tr -d '\n'; printf '\a'; } > /dev/tty

.local/bin/pbpaste

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# pbpaste -- companion to pbcopy.
+#
+# Terminals almost universally refuse OSC 52 *reads* (it would let any remote
+# program siphon your clipboard), so this cannot see your local clipboard.
+# What it can do is echo back the tmux paste buffer, i.e. whatever pbcopy or
+# a tmux copy-mode yank last put there.
+
+set -euo pipefail
+
+if [[ -n "${DISPLAY:-}" ]] && command -v xclip >/dev/null 2>&1; then
+    exec xclip -selection clipboard -o
+fi
+if [[ -n "${WAYLAND_DISPLAY:-}" ]] && command -v wl-paste >/dev/null 2>&1; then
+    exec wl-paste
+fi
+if [[ -n "${TMUX:-}" ]] && command -v tmux >/dev/null 2>&1; then
+    exec tmux save-buffer -
+fi
+
+echo "pbpaste: no readable clipboard (not in tmux, no display)" >&2
+exit 1

.tmux.conf

@@ -128,6 +128,13 @@ bind-key -T copy-mode-vi 'C-l' select-pane -R
 bind-key -T copy-mode-vi 'C-\' select-pane -l
 
 
+# Clipboard (OSC 52)
+# Required for nested tmux (local tmux -> ssh/mosh -> remote tmux): the inner
+# tmux sends its copies up as OSC 52, and tmux only accepts OSC 52 coming
+# from a pane when set-clipboard is "on". The default "external" drops it.
+set -g set-clipboard on
+set -as terminal-features ',*:clipboard'
+
 #
 # Initialize TMUX plugin manager (keep this line at the very bottom of tmux.conf)
 run '~/.tmux/plugins/tpm/tpm'