refactor(meta): flatten groups; only break out optional/hw-specific

Drop the per-domain group fragmentation in meta/ and the parallel
group-per-file structure in systemd-units/.

  meta/ (18 -> 6 groups):
    keep    base, flatpak (magic), intel, nvidia, work, btc
    fold    browser, bt, cpp, dev, extra, fonts, mail, media, nix,
            sound, wayland -> base (with `# --- section ---` comments
            preserving at-a-glance structure)
    drop    fortran (niche; install ad-hoc when needed)

  systemd-units/:
    flatten to a single system.txt + user.txt; .ignore files move up
    one level; group concept and pairing rule removed.

  justfile:
    unit-list/unit-apply/unit-status no longer take a group argument.
    unit-add/unit-forget infer scope by probing
    `systemctl [--user] cat <unit>` (system wins on tie). Top-level
    add/forget dispatcher updated: any unit-suffixed arg routes to
    unit-* without requiring a leading GROUP.

  docs:
    .github/copilot-instructions.md and README.md updated to describe
    the new flat layout. Pairing rule and group-token grammar gone.

Pure layout refactor - no package contents change.

13 files changed, 180 insertions, 173 deletions

diff --git a/meta/base.txt b/meta/base.txt
index 9c56e52..81b93c7 100644
--- a/meta/base.txt
+++ b/meta/base.txt
@@ -1,3 +1,4 @@
+# --- core ---
 acpid
 base
 base-devel
@@ -66,3 +67,182 @@ zsh-completions
 zsh-history-substring-search
 zsh-syntax-highlighting
 zram-generator
+
+# --- bluetooth ---
+bluez
+bluez-utils
+ell
+
+# --- nix (multi-user daemon mode for hermetic per-project dev shells via
+# `nix develop` + direnv `use flake`. Not a replacement for paru/pacman,
+# not home-manager, not NixOS — just a sandboxed second package manager
+# that gives every project a reproducible toolchain pinned in its own
+# flake.lock. Pairs with: systemd-units/system.txt (enables
+# nix-daemon.socket), etc/nix/nix.conf, dot_config/direnv/direnvrc,
+# dot_config/nix/templates/. nix-direnv itself is loaded at runtime via
+# direnv's source_url with a content hash, so no extra package needed.) ---
+nix
+
+# --- dev ---
+android-tools
+ccache
+clang
+cmake
+curl
+difftastic
+direnv
+doxygen
+gdb
+git-absorb
+git-delta
+github-cli
+go
+hyperfine
+jdk-openjdk
+just
+lld
+lldb
+luarocks
+mergiraf
+mold
+ninja
+npm
+perf
+podman-compose
+podman-docker
+rust-analyzer
+rustup
+samply
+sccache
+strace
+t-rec
+uv
+valgrind
+
+# --- sound ---
+alsa-utils
+pipewire
+pipewire-alsa
+pipewire-jack
+pipewire-pulse
+playerctl
+pulsemixer
+# noisetorch  # optional
+
+# --- fonts ---
+noto-fonts-emoji
+otf-font-awesome
+otf-latinmodern-math
+ttf-dejavu
+ttf-fira-code
+ttf-font-awesome
+ttf-noto-nerd
+woff2-font-awesome
+
+# --- wayland session ---
+# Compositor
+sway
+xdg-desktop-portal-wlr
+xdg-desktop-portal-gtk
+qt5-wayland
+qt6-wayland
+
+# Bar & launcher
+waybar
+fuzzel
+# wofi: secondary picker used only by mako-history.sh — needs --hide-search
+# and per-key custom bindings, neither of which fuzzel supports.
+wofi
+
+# Terminal
+ghostty
+
+# Notifications
+mako
+libnotify
+poweralertd
+
+# Lock screen
+swaylock
+swayidle
+
+# Clipboard
+wl-clipboard
+cliphist
+
+# Screenshots & recording
+grim
+slurp
+wf-recorder
+
+# Wayland typing (used by dictate, etc)
+wtype
+
+# Emoji picker (AUR; tiny shell script, multi-backend — we drive it through wofi)
+bemoji
+
+# Image viewer
+imv
+
+# QR
+zbar
+xorg-xwayland # needed for zbarcam's X11 preview
+
+# Document viewer is the org.pwmt.zathura flatpak (see meta/flatpak.txt) so
+# PDFs handed off from the browser/mail sandbox stay sandboxed.
+
+# Misc
+brightnessctl
+libfido2
+perl-file-mimeinfo
+qt5ct
+qt6ct
+xdg-user-dirs
+wl-mirror
+
+# --- browser (LibreWolf flatpak; arkenfox-user.js is the host-side
+# hardening overlay deployed by run_onchange_after_deploy-firefox.sh.tmpl) ---
+arkenfox-user.js
+
+# --- mail (host-side bits the org.mozilla.Thunderbird flatpak depends on) ---
+protonmail-bridge-core
+# git send-email Perl prereqs (SMTP via local Bridge on 127.0.0.1:1025)
+perl-authen-sasl
+perl-mime-tools
+perl-net-smtp-ssl
+# Native messaging host binary for External Editor Revived; bridged into
+# the TB flatpak by run_onchange_after_deploy-tb-eer.sh.tmpl.
+external-editor-revived
+
+# --- media (native mpv kept for streamlink piping and the /tmp/mpvsocket
+# IPC integration; the io.mpv.Mpv flatpak (meta/flatpak.txt) is set as
+# the mimeapps default for video/* so files handed off by the
+# browser/mail sandbox stay sandboxed) ---
+mpv
+streamlink
+yt-dlp
+
+# --- desktop extras ---
+gpg-tui
+pandoc-bin
+syncthing
+udisks2
+
+# Flatpak runtime (apps tracked in meta/flatpak.txt)
+flatpak
+
+# Smartcard stack (cartão de cidadão reader + PKCS#11 bridge into flatpak
+# browsers). pcscd.socket is enabled by systemd-units/system.txt.
+pcsclite
+ccid
+
+# OCR (used by ~/.local/bin/ocr)
+tesseract
+tesseract-data-eng
+tesseract-data-por
+
+# Speech-to-text (used by ~/.local/bin/dictate)
+# `base` multilingual: ~142 MB, ~7-10x realtime on a 4c CPU. Override
+# WHISPER_MODEL in the script's environment to use a different ggml model.
+whisper.cpp-vulkan
+whisper.cpp-model-base
diff --git a/meta/browser.txt b/meta/browser.txt
deleted file mode 100644
index de2d297..0000000
--- a/meta/browser.txt
+++ /dev/null
@@ -1 +0,0 @@
-arkenfox-user.js
diff --git a/meta/bt.txt b/meta/bt.txt
deleted file mode 100644
index d835748..0000000
--- a/meta/bt.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-bluez
-bluez-utils
-ell
diff --git a/meta/cpp.txt b/meta/cpp.txt
deleted file mode 100644
index e4e11f6..0000000
--- a/meta/cpp.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-ccache
-clang
-cmake
-doxygen
-gdb
-lld
-lldb
-ninja
-perf
-valgrind
diff --git a/meta/dev.txt b/meta/dev.txt
deleted file mode 100644
index 5f26ad7..0000000
--- a/meta/dev.txt
+++ /dev/null
@@ -1,24 +0,0 @@
-android-tools
-curl
-difftastic
-direnv
-git-absorb
-git-delta
-github-cli
-go
-hyperfine
-jdk-openjdk
-just
-luarocks
-mergiraf
-mold
-npm
-podman-compose
-podman-docker
-rust-analyzer
-rustup
-samply
-sccache
-strace
-t-rec
-uv
diff --git a/meta/extra.txt b/meta/extra.txt
deleted file mode 100644
index 956d0c1..0000000
--- a/meta/extra.txt
+++ /dev/null
@@ -1,23 +0,0 @@
-gpg-tui
-pandoc-bin
-syncthing
-udisks2
-
-# Flatpak runtime (apps tracked in meta/flatpak.txt)
-flatpak
-
-# Smartcard stack (cartão de cidadão reader + PKCS#11 bridge into flatpak browsers).
-# pcscd.socket is enabled by systemd-units/system/base.txt.
-pcsclite
-ccid
-
-# OCR (used by ~/.local/bin/ocr)
-tesseract
-tesseract-data-eng
-tesseract-data-por
-
-# Speech-to-text (used by ~/.local/bin/dictate)
-# `base` multilingual: ~142 MB, ~7-10x realtime on a 4c CPU. Override
-# WHISPER_MODEL in the script's environment to use a different ggml model.
-whisper.cpp-vulkan
-whisper.cpp-model-base
diff --git a/meta/fonts.txt b/meta/fonts.txt
deleted file mode 100644
index 603fb44..0000000
--- a/meta/fonts.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-noto-fonts-emoji
-otf-font-awesome
-otf-latinmodern-math
-ttf-dejavu
-ttf-fira-code
-ttf-font-awesome
-ttf-noto-nerd
-woff2-font-awesome
diff --git a/meta/fortran.txt b/meta/fortran.txt
deleted file mode 100644
index 4bb1d35..0000000
--- a/meta/fortran.txt
+++ /dev/null
@@ -1,3 +0,0 @@
-fortitude-bin
-fortran-fpm-bin
-gcc-fortran
diff --git a/meta/mail.txt b/meta/mail.txt
deleted file mode 100644
index 74f6214..0000000
--- a/meta/mail.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-# Host-side bits the org.mozilla.Thunderbird flatpak depends on.
-protonmail-bridge-core
-# git send-email Perl prereqs (SMTP via local Bridge on 127.0.0.1:1025)
-perl-authen-sasl
-perl-mime-tools
-perl-net-smtp-ssl
-# Native messaging host binary for External Editor Revived; bridged into the
-# TB flatpak by run_onchange_after_deploy-tb-eer.sh.tmpl.
-external-editor-revived
diff --git a/meta/media.txt b/meta/media.txt
deleted file mode 100644
index 8e5b5c2..0000000
--- a/meta/media.txt
+++ /dev/null
@@ -1,7 +0,0 @@
-# Native mpv is kept for streamlink piping and the /tmp/mpvsocket IPC
-# integration; the io.mpv.Mpv flatpak (meta/flatpak.txt) is set as the
-# mimeapps default for video/* so files handed off by the browser/mail
-# sandbox stay sandboxed.
-mpv
-streamlink
-yt-dlp
diff --git a/meta/nix.txt b/meta/nix.txt
deleted file mode 100644
index e5c4bb4..0000000
--- a/meta/nix.txt
+++ /dev/null
@@ -1,16 +0,0 @@
-# Nix package manager (multi-user daemon mode).
-#
-# Used purely for hermetic per-project dev shells via `nix develop` +
-# direnv `use flake`. Not a replacement for paru/pacman, not home-manager,
-# not NixOS — just a sandboxed second package manager that gives every
-# project a reproducible toolchain pinned in its own flake.lock.
-#
-# Pairs with:
-#   - systemd-units/system/nix.txt  (enables nix-daemon.socket)
-#   - etc/nix/nix.conf              (flakes, trusted-users=@wheel, GC roots)
-#   - dot_config/direnv/direnvrc    (loads nix-direnv; pinned via source_url)
-#   - dot_config/nix/templates/     (flake templates: nix flake init -t ~/.config/nix/templates)
-#
-# nix-direnv itself is not packaged for Arch — it's loaded at runtime via
-# direnv's source_url with a content hash, so no extra package needed.
-nix
diff --git a/meta/sound.txt b/meta/sound.txt
deleted file mode 100644
index 5e9c45e..0000000
--- a/meta/sound.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-alsa-utils
-pipewire
-pipewire-alsa
-pipewire-jack
-pipewire-pulse
-playerctl
-pulsemixer
-
-# Optional
-# noisetorch
diff --git a/meta/wayland.txt b/meta/wayland.txt
deleted file mode 100644
index b41668b..0000000
--- a/meta/wayland.txt
+++ /dev/null
@@ -1,59 +0,0 @@
-# Compositor
-sway
-xdg-desktop-portal-wlr
-xdg-desktop-portal-gtk
-qt5-wayland
-qt6-wayland
-
-# Bar & launcher
-waybar
-fuzzel
-# wofi: secondary picker used only by mako-history.sh — needs --hide-search
-# and per-key custom bindings, neither of which fuzzel supports.
-wofi
-
-# Terminal
-ghostty
-
-# Notifications
-mako
-libnotify
-poweralertd
-
-# Lock screen
-swaylock
-swayidle
-
-# Clipboard
-wl-clipboard
-cliphist
-
-# Screenshots & recording
-grim
-slurp
-wf-recorder
-
-# Wayland typing (used by dictate, etc)
-wtype
-
-# Emoji picker (AUR; tiny shell script, multi-backend — we drive it through wofi)
-bemoji
-
-# Image viewer
-imv
-
-# QR
-zbar
-xorg-xwayland # needed for zbarcam's X11 preview
-
-# Document viewer is the org.pwmt.zathura flatpak (see meta/flatpak.txt) so
-# PDFs handed off from the browser/mail sandbox stay sandboxed.
-
-# Misc
-brightnessctl
-libfido2
-perl-file-mimeinfo
-qt5ct
-qt6ct
-xdg-user-dirs
-wl-mirror