Configure tmux and keep the iTerm2 tab titles working inside it

[mattmenefee]

Summary

• Adds home/.tmux.conf, the first tmux configuration in this repo, and records tmux in the Brewfile — it was installed on this machine but never tracked, so a fresh machine got the ta alias without the binary behind it.
• Fixes ta, which has never worked when no session was running: it falls back to tn, and nothing defined tn — not this repo, and not the oh-my-zsh tmux plugin (which is not in the plugin list and defines tksv/tl/tmuxconf/tds instead). Adds tn, plus tm for attach-or-create against a fixed session name.
• Makes home/.zsh/iterm2-tab-title.zsh tmux-aware. Without this, adding a tmux config would have silently killed the tab titles: that file emits OSC 1, and tmux discards OSC 1 while acting on OSC 2. Titles now go out as OSC 2 inside a pane, and set-titles-string "#T" republishes them to iTerm2 unchanged. The SetUserVar sequence carrying the directory is wrapped in tmux's DCS passthrough for the same reason, which is what allow-passthrough on in the config enables.

On the config's contents

Most of it is conventional — mouse support, a large scrollback, 1-indexed windows that renumber on close, vi copy keys, splits that inherit the pane's directory, vim's home row for pane movement, and a status line on bg=default so it inherits the terminal background instead of fighting the active iTerm2 profile.

The settings were picked against tmux 3.7's measured defaults rather than the ones most guides still quote:

Setting	Why it's here
escape-time 10	Already the default in current tmux, but it sat at 500ms for years. Pinned so an older tmux doesn't reintroduce a visible delay in front of every Esc.
mode-keys vi	Already inferred from $EDITOR="mvim -v". Pinned so copy mode doesn't change keys if $EDITOR does.
set-clipboard on	The outbound half (yank → terminal clipboard, including through SSH) already works at the default external. on adds the inbound half, letting an application in a pane populate a tmux buffer over OSC 52.
aggressive-resize on	The one genuine behavior change: windows size to the smallest client actually viewing them rather than the smallest client attached at all, so a second, smaller client stops shrinking the first one's panes.

Note on activation

home/.tmux.conf is a new top-level file rather than a member of an already-symlinked directory, so it needs a homesick link run (or a single symlink) before it takes effect.

Test plan

• tmux -f home/.tmux.conf new-session -d loads with no config errors on tmux 3.7c
• ~/.tmux.conf symlink resolves, and a default-path tmux server reads back allow-passthrough=on, aggressive-resize=on, set-titles-string=#T — none of which are defaults
• Inside tmux, _tab_title_idle sets pane_title to the git branch (main), and _tab_title_running rspec sets it to ▶ rspec
• Outside tmux, _tab_title_emit emits the original OSC 1 byte-for-byte (^[]1;BRANCH^G)
• OSC 1 vs OSC 2 handling confirmed empirically against a live tmux server rather than from the manual
• All six zsh files pass zsh -n, the same gate CI runs
• ta, tn, and tm all resolve in a fresh zsh
• In a real iTerm2 window: a tab inside tmux shows the branch when idle and ▶ cmd while a command runs, and user.dir keeps updating through the DCS passthrough
• brew bundle reconciles the new tmux entry