feat(autotheme): fire at the configured sunrise/sunset, not a 15-min poll

The timer's OnCalendar now bakes the configured times (falling back
like _hhmm_to_min on a hand-edited state), so the switch lands at the
configured minute instead of up to 15 minutes late. The original
poll's robustness case is covered without it: Persistent catches
transitions missed while powered off, systemd fires elapsed calendar
timers on resume, and OnStartupSec settles the theme after login.

Baked times mean a time edit must rebuild: the menu's Sunrise/Sunset
writes now run `auto --force` when enabled (one rebuild re-bakes the
timer and lands on the right theme, same as the enable flow). Day and
night slugs stay live reads — but with no poll to catch them up,
editing the slot currently on screen applies immediately via a plain
`auto`. New eval check `auto-theme-timer` asserts the bake
state-bridges-style: configured times reach OnCalendar, garbage falls
back to 07:00/20:00, disabled installs no unit. Docs + hardware-queue
entry updated to the new semantics.

V2: checks.auto-theme (KVM VM, passed) covers the auto engine the
timer ticks; checks.auto-theme-timer (eval, passed) covers the unit;
OnCalendar strings systemd-analyze-validated; the rebuilt menu script
passes bash -n with the new branches in place. V3 pending: live timer
firing at the exact configured minute on hardware (existing
"Auto-theme pair flip" queue entry, refreshed).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

modules/home/rofi.nix

@@ -962,13 +962,16 @@ ${lib.concatStringsSep "\n" (lib.mapAttrsToList
       autotheme)
         # Look & Feel › Auto theme — automatic day/night theme switch
         # (settings.autoTheme, applied by the nomarchy-auto-theme timer from
-        # autotheme.nix). The enable flag GATES the timer's install, so
-        # turning it *on* must rebuild; day/night/times are read live by
-        # `nomarchy-state-sync auto`, so those writes are instant
-        # (--no-switch). Enabling writes the flag then `auto --force`, so a
-        # single rebuild both installs the timer and applies the right theme
-        # now. Disabling is instant: the flag flips and `auto` self-gates to
-        # a no-op, so the lingering timer does nothing until the next rebuild.
+        # autotheme.nix). The enable flag GATES the timer's install and the
+        # sunrise/sunset times are BAKED into its OnCalendar, so turning it
+        # *on* or editing a time must rebuild — both run `auto --force`, so
+        # one rebuild re-bakes the timer AND lands on the right theme now.
+        # Day/night slugs are read live by `nomarchy-state-sync auto`, so
+        # those writes are instant (--no-switch); when the edited slot is the
+        # one on screen, a plain `auto` applies it right away (the timer only
+        # fires at the next transition — there is no poll to catch it up).
+        # Disabling is instant: the flag flips and `auto` self-gates to a
+        # no-op, so the lingering timer does nothing until the next rebuild.
         at_get() { nomarchy-state-sync get "settings.autoTheme.$1" 2>/dev/null; }
         en=$(at_get enable); day=$(at_get day); night=$(at_get night)
         sunrise=$(at_get sunrise); sunset=$(at_get sunset)
@@ -997,15 +1000,20 @@ ${lib.concatStringsSep "\n" (lib.mapAttrsToList
             nomarchy-state-sync --quiet set settings.autoTheme.enable true --no-switch
             notify-send "Auto theme" "On — applying the theme for now…"
             exec nomarchy-state-sync auto --force ;;   # one rebuild: install timer + apply
-          "Day theme"*)
-            slug=$( { nomarchy-state-sync list; printf '%s\n' "$BACK"; } | rofi_menu -p "Day theme") || exec "$0" autotheme
-            [ "$slug" != "$BACK" ] && [ -n "$slug" ] \
-              && nomarchy-state-sync --quiet set settings.autoTheme.day "$slug" --no-switch
-            exec "$0" autotheme ;;
-          "Night theme"*)
-            slug=$( { nomarchy-state-sync list; printf '%s\n' "$BACK"; } | rofi_menu -p "Night theme") || exec "$0" autotheme
-            [ "$slug" != "$BACK" ] && [ -n "$slug" ] \
-              && nomarchy-state-sync --quiet set settings.autoTheme.night "$slug" --no-switch
+          "Day theme"*|"Night theme"*)
+            key=day; label="Day theme"
+            case "$choice" in "Night theme"*) key=night; label="Night theme" ;; esac
+            slug=$( { nomarchy-state-sync list; printf '%s\n' "$BACK"; } | rofi_menu -p "$label") || exec "$0" autotheme
+            if [ "$slug" != "$BACK" ] && [ -n "$slug" ]; then
+              nomarchy-state-sync --quiet set "settings.autoTheme.$key" "$slug" --no-switch
+              # Edited the slot that is on screen right now? Apply it — the
+              # timer won't fire again until the next sunrise/sunset.
+              if [ "$en" = true ] && [ "$(nomarchy-state-sync auto --which)" = "$slug" ] \
+                 && [ "$(nomarchy-state-sync get slug)" != "$slug" ]; then
+                notify-send "Auto theme" "$label: $slug — applying…"
+                exec nomarchy-state-sync auto
+              fi
+            fi
             exec "$0" autotheme ;;
           "Sunrise"*|"Sunset"*)
             key=sunrise; label=Sunrise; cur="''${sunrise:-07:00}"
@@ -1014,7 +1022,14 @@ ${lib.concatStringsSep "\n" (lib.mapAttrsToList
             case "$t" in
               ""|"$BACK") : ;;
               [01][0-9]:[0-5][0-9]|2[0-3]:[0-5][0-9])
-                nomarchy-state-sync --quiet set "settings.autoTheme.$key" "$t" --no-switch ;;
+                nomarchy-state-sync --quiet set "settings.autoTheme.$key" "$t" --no-switch
+                # The time is baked into the timer's OnCalendar, so a change
+                # must rebuild; `auto --force` is that rebuild AND lands on
+                # the right theme for the new schedule in the same pass.
+                if [ "$en" = true ]; then
+                  notify-send "Auto theme" "$label $t — rebuilding the schedule…"
+                  exec nomarchy-state-sync auto --force
+                fi ;;
               *) notify-send "Auto theme" "Ignored '$t' — use HH:MM (24-hour)." ;;
             esac
             exec "$0" autotheme ;;