The interactive init is small; four fragment files was over-splitting it.
Keep the mechanic (a real fish file inlined by Nix into config.fish) but
merge the fragments into a single modules/fish/config.fish read with
builtins.readFile. Rendered config is unchanged.
Break the interactive init into concern-scoped fish files under
modules/fish/config/ (bindings, env, done, path) and assemble them with
lib.concatMapStringsSep + readFile into a single interactiveShellInit, so
home-manager still writes one ~/.config/fish/config.fish. The pieces stay
editable as separate fish files; the rendered file is unchanged.
Fold the done plugin tuning back into config.fish and drop the conf.d
fragment: config.fish is read whole into interactiveShellInit, so Nix
assembles the interactive init at build time instead of fish autoloading
a separate conf.d file. functions/copy.fish stays a function file, the
idiomatic home for a lazily-autoloaded function.
Move the Module to modules/fish/fish.nix and mirror a real fish config
directory beside it: config.fish (interactive init), conf.d/done.fish
(the done plugin tuning, now a real conf.d file), and functions/copy.fish.
completions/ and themes/ are omitted as they have no content and git
cannot track empty directories.
Move the login-shell switch behind a new modules.fish.defaultShell
option (default false; neogaia opts in). Convert every non-eza alias to
an abbreviation, set preferAbbrs and pin generateCompletions, and switch
the command line to vi-style editing. Cap navigation at four dots and
drop psmem/psmem10/dir/vdir/please. Comment the installed packages.
Translate the CachyOS fish snapshot into a home-manager Module: the
fastfetch greeting, the bat-backed manpager, the done and bang-bang
plugins (from nixpkgs, not a plugin manager), the history/backup/copy
helper functions, and the eza and navigation aliases. Pacman-specific
aliases are dropped or replaced with NixOS equivalents (update ->
nixos-rebuild switch, cleanup -> nix-collect-garbage). Enabling the
Module also makes fish the user's default login shell.
