style: align comments with the project conventions

Apply a codebase-wide comment audit against the comment conventions:
split banned semicolons and multi-sentence lines into one sentence per
line, cut cross-file and history narration, trim file-top headers to a
single purpose line, and drop verbosity that did not earn its place.
Prose docs (CLAUDE.md, install.md) get the same one-sentence-per-line
and no-semicolon treatment.

modules/tmux/tmux.nix

@@ -3,8 +3,8 @@
   lib,
   ...
 }:
-# tmux for the primary user, configured through home-manager. Settings without a
-# home-manager option are read from ./extra.conf.
+# tmux for the primary user, configured through home-manager.
+# Settings without a home-manager option are read from ./extra.conf.
 let
   cfg = config.modules.tmux;
   user = config.user.name;