feat(menu): one fingerprint switch, an auto-login toggle, and the state bridge they needed

Bernardo, post-reboot: "Use for login" was the wrong question. Whether the
finger works is one decision, not two, and whether login prompts at all is
a different decision that was never in the menu.

System › Fingerprint is now a single Fingerprint (on/off) switch, leading
the menu with enroll/list/verify/delete as the plumbing behind it. It
writes the one settings.fingerprint.pam key, and modules/home/idle.nix now
defaults idle.fingerprint from that same key — so the lock screen and
login/sudo move together instead of drifting apart the way they did until
e2de906. nomarchy-fingerprint does the two rebuilds this needs (sudo
system for PAM, home switch for hyprlock) and refuses to turn on with no
finger enrolled.

System › Auto-login is new (nomarchy-autologin), and it is what decides
whether anything is asked at boot: auto-login on means no prompt whatever
the fingerprint switch says; off means the greeter asks, for a password or
a finger. Installer-seeded ON for LUKS machines — the passphrase already
gates the disk — and off without it, where the greeter is the only thing
between power-on and the desktop.

Both had to become state-owned to be toggleable at all, which surfaced two
real bugs:

  * nomarchy.system.greeter.autoLogin defaulted from
    `config.nomarchy.settings…` — an attribute that exists ONLY on the Home
    Manager side. On NixOS it is absent and `or null` swallowed the error,
    so the default silently evaluated to null on every machine ever built.
    That is why the installer baked a Nix line: the state path never
    worked. Now read via theme-state-read.nix (the hardware.nix/timezone.nix
    pattern) and mkDefault'd, so the menu owns it and a hand-set line still
    pins it. Two more options read the same phantom bridge — BACKLOG #116.
  * `theme-sync get` printed Python's "None" for a JSON null, so every
    `case … null)` a caller writes would miss. Now prints "null", as the
    comment above it already promised for booleans.

The installer seeds the state instead of emitting the system.nix line,
because that line outranks the state and would strand the toggle.

V1 (V3 pending: HARDWARE-QUEUE). nix flake check --no-build, installer-
safety and option-docs all pass. Proved by eval/build, not assumed: a state
carrying autoLogin yields greetd initial_session {"user":"bernardo"}, the
template state (no autoLogin) yields none, and a hand-set null beats a state
that says otherwise; a state with only fingerprint.pam=true — nothing set by
hand — renders the hyprlock auth.fingerprint block; both new tools pass
bash -n and land in systemPackages (nomarchy-fingerprint only with a
reader); the patcher writes settings.greeter.autoLogin and no system.nix
line; and the get round trip prints null, so the menu reads "Auto-login
(off)" where it would have read "(on)".

The reader itself, the two rebuilds, and the reboot are hardware — queued.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/rofi.nix

@@ -901,6 +901,16 @@ ${themeRows}
           || { notify-send "Auto timezone" "Unavailable on this machine."; exit 0; }
         exec ${cfg.terminal} -e nomarchy-autotimezone toggle ;;
 
+      autologin)
+        # Toggle booting straight into the session (greetd initial_session).
+        # A SYSTEM setting baked at rebuild, so this sudos a system switch in
+        # a terminal, like Auto timezone — and the change shows on the NEXT
+        # boot, not now. Off is what makes the greeter ask for a password (or
+        # a finger, when System › Fingerprint is on).
+        command -v nomarchy-autologin >/dev/null 2>&1 \
+          || { notify-send "Auto-login" "Unavailable on this machine."; exit 0; }
+        exec ${cfg.terminal} -e nomarchy-autologin toggle ;;
+
       autocommit)
         # Toggle opt-in auto-commit: every menu/theme mutation also commits
         # theme-state.json (that file only) in the downstream flake, so
@@ -977,13 +987,17 @@ ${themeRows}
         command -v fprintd-list >/dev/null 2>&1 \
           || { notify-send "Fingerprint" "fprintd not available (nomarchy.hardware.fingerprint.enable?)."; exit 0; }
         pam=$(nomarchy-theme-sync get settings.fingerprint.pam 2>/dev/null || echo false)
-        case "$pam" in true|True) pam_label="Use for login (on)" ;; *) pam_label="Use for login (off)" ;; esac
+        case "$pam" in true|True) pam_label="Fingerprint (on)" ;; *) pam_label="Fingerprint (off)" ;; esac
         choice=$( {
+          # The switch leads: it is the decision this menu exists for, and
+          # the rest (enroll/list/verify/delete) is the plumbing behind it —
+          # all still usable while the switch is off, since turning it on
+          # requires an enrolled finger.
+          row "$pam_label"        system-lock-screen
           row "Enroll finger"     preferences-desktop-user-password
           row "List enrolled"     view-list
           row "Verify"            dialog-password
           row "Delete all"        edit-delete
-          row "$pam_label"        system-lock-screen
           back
         } | rofi_menu -show-icons -p Fingerprint) || exit 0
         case "$choice" in
@@ -1013,17 +1027,15 @@ ${themeRows}
                 *)   echo "Cancelled." ;;
               esac
               printf "\nEnter to close."; read -r _' ;;
-          *"Use for login"*)
-            case "$pam" in true|True) new=false ;; *) new=true ;; esac
-            if [ "$new" = true ]; then
-              if fprintd-list "$USER" 2>/dev/null | grep -qiE 'no fingers enrolled|No devices available'; then
-                notify-send "Fingerprint" "Enroll a finger first, then enable login."
-                exit 0
-              fi
-            fi
-            nomarchy-theme-sync --quiet set settings.fingerprint.pam "$new" --no-switch
-            notify-send "Fingerprint" "Use for login: $new — applies on next nomarchy-rebuild."
-            ;;
+          *"Fingerprint ("*)
+            # Drives BOTH sides off one state key (sudo/login PAM + the
+            # hyprlock unlock), so it sudos a system rebuild and runs a home
+            # switch — in a terminal, like Auto timezone. The enrolled-finger
+            # guard and the state write live in the tool, so the CLI and this
+            # row can't disagree.
+            command -v nomarchy-fingerprint >/dev/null 2>&1 \
+              || { notify-send "Fingerprint" "nomarchy-fingerprint not on PATH (hardware.fingerprint.enable?)."; exit 0; }
+            exec ${cfg.terminal} -e nomarchy-fingerprint toggle ;;
         esac ;;
 
       controlcenter)
@@ -1139,6 +1151,17 @@ ${themeRows}
           then row "Auto timezone (on)"  preferences-system-time
           else row "Auto timezone (off)" preferences-system-time
           fi
+          # Auto-login — self-gated on the tool (greeter.enable). Off = the
+          # greeter asks; that's the prompt the Fingerprint switch feeds.
+          if command -v nomarchy-autologin >/dev/null 2>&1; then
+            # Unset (get exits 1, empty) and null both read as off. "None" is
+            # what an older theme-sync printed for null — accepted so a menu
+            # from a newer generation can't misreport against an older tool.
+            case "$(nomarchy-theme-sync get settings.greeter.autoLogin 2>/dev/null)" in
+              null|""|None) row "Auto-login (off)" system-users ;;
+              *)            row "Auto-login (on)"  system-users ;;
+            esac
+          fi
           if [ -e "''${NOMARCHY_PATH:-$HOME/.nomarchy}/.git" ]; then
             if [ "$(nomarchy-theme-sync get settings.autoCommit 2>/dev/null)" = true ]
             then row "Auto-commit (on)"  git
@@ -1178,6 +1201,7 @@ ${themeRows}
           *Printers*)         exec "$0" printers ;;
           *"Do Not Disturb"*) exec "$0" dnd ;;
           *"Auto timezone"*)  exec "$0" autotimezone ;;
+          *"Auto-login"*)     exec "$0" autologin ;;
           *"Auto-commit"*)    exec "$0" autocommit ;;
           *Snapshots*)        exec "$0" snapshot ;;
           *Rollback*)         exec "$0" rollback ;;
@@ -1294,7 +1318,7 @@ ${themeRows}
         esac ;;
 
       *)
-        echo "usage: nomarchy-menu [lookfeel|tools|system|power|power-profile|powermgmt|batterylimit|theme|clipboard|calc|files|emoji|web|network|bluetooth|audio|display|display-profile|keyboard|printers|capture|colorpicker|keybinds|ask|dnd|nightlight|autotimezone|autocommit|vpn|snapshot|doctor|firmware|fingerprint|controlcenter|rollback|whatchanged]" >&2
+        echo "usage: nomarchy-menu [lookfeel|tools|system|power|power-profile|powermgmt|batterylimit|theme|clipboard|calc|files|emoji|web|network|bluetooth|audio|display|display-profile|keyboard|printers|capture|colorpicker|keybinds|ask|dnd|nightlight|autotimezone|autologin|autocommit|vpn|snapshot|doctor|firmware|fingerprint|controlcenter|rollback|whatchanged]" >&2
         exit 64 ;;
     esac
   '';