fix(idle): skip DPMS-off when docked (#127 mitigation)

Blanking the only live output in dock mode led to a brick where wake and
even VT switch failed. Skip hypridle's 10m dpms off when any laptop
internal (eDP/LVDS/DSI) is present but not enabled; lock at 5m remains.
Undocked still blanks. Document LATER revisit for intentional
DPMS-when-docked once wake is proven.

V1: nix flake check --no-build. V3: docked idle stays lit under lock.

modules/home/idle.nix

@@ -20,24 +20,10 @@ let
     exit 1
   '';
 
-  # Same transition binary hyprland.nix puts on PATH — re-derived here so
-  # hypridle can pin absolute store paths (thin PATH in the user unit).
-  # Must stay in lockstep with modules/home/hyprland.nix's transition.
-  # We only need undock/enable + dpms; call via PATH-installed name is
-  # fragile, so wake embeds the transition from a minimal import chain:
-  # dump+wake live in display-tools.nix; transition is the public name
-  # on PATH after HM activation — wake script uses absolute path from
-  # a local reimplementation of just the enable/dpms rescue when the
-  # full transition package isn't injectable without circular imports.
-  #
-  # Practical approach: invoke `nomarchy-display-wake` from PATH after
-  # activation; for the unit Exec lines use a wrapper that prefers the
-  # store path of a wake script built with transition = null fallback
-  # (hyprctl keyword + reload + dpms) matching undock's public contract.
+  # Absolute store paths for hypridle (thin PATH). Wake reuses the shared
+  # helper; a mini transition avoids a circular import on hyprland.nix.
   displayWake =
     let
-      # Minimal undock-equivalent for idle's store path (no circular dep on
-      # hyprland.nix). Prefer the real transition when on PATH at runtime.
       miniTransition = pkgs.writeShellScriptBin "nomarchy-display-transition" ''
         set -u
         case "''${1:-}" in
@@ -65,6 +51,31 @@ let
       inherit pkgs;
       displayTransition = miniTransition;
     }).displayWakeTool;
+
+  # #127 mitigation (2026-07-15): blanking the *only* live output while
+  # docked (eDP disabled) left a black seat that sometimes would not
+  # recover (and even VT switch looked dead). Skip DPMS-off when any
+  # laptop internal is present but not enabled. Lock still runs at 5 min.
+  # Revisit: intentional DPMS-on-dock once wake is trustworthy — see
+  # BACKLOG #127 and LATER "DPMS when docked".
+  dpmsOff = pkgs.writeShellScript "nomarchy-dpms-off" ''
+    set -euo pipefail
+    jq=${pkgs.jq}/bin/jq
+    internals=$(hyprctl monitors all -j 2>/dev/null \
+      | $jq -r '.[] | select(.name | test("^(eDP|LVDS|DSI)")) | .name' \
+      2>/dev/null || true)
+    if [ -n "$internals" ]; then
+      for m in $internals; do
+        if ! hyprctl monitors -j 2>/dev/null \
+              | $jq -e --arg m "$m" 'any(.[]; .name == $m)' >/dev/null 2>&1; then
+          ${pkgs.util-linux}/bin/logger -t nomarchy-idle -- \
+            "dpms-off skipped: docked (internal $m not enabled)"
+          exit 0
+        fi
+      done
+    fi
+    hyprctl dispatch dpms off
+  '';
 in
 {
   config = lib.mkIf cfg.idle.enable {
@@ -168,8 +179,8 @@ in
           { timeout = 300; on-timeout = "loginctl lock-session"; }
           {
             timeout = 600;
-            on-timeout = "hyprctl dispatch dpms off";
-            # Same rescue path as after_sleep (#127).
+            # Docked: skip blanking sole output (#127). Undocked: DPMS off.
+            on-timeout = "${dpmsOff}";
             on-resume = "${lib.getExe displayWake}";
           }
           # Suspend only on battery, and sooner than the old fixed 30 min