Cut restated "what", domain-glossary framing, cross-file consumption
narration, and against-alternative justification from in-file comments;
keep only non-obvious "why" and load-bearing pointers. Drop the
`generateCompletions` line (a no-op restatement of the upstream default)
and its comment.
Configure tmux through home-manager's programs.tmux: the settings it exposes
as options (prefix, keyMode, mouse, baseIndex, clock24, escapeTime,
historyLimit, terminal) are set as options, and every setting it has no option
for is read verbatim from modules/tmux/extra.conf. No tmux plugin manager is
used. The generated config is behaviourally identical to the reference, verified
by parsing it with a live tmux binary.
