refactor(display): extract the shared display-transition + keyboard tools (#150)

The full nomarchy-display-transition (dock/undock/enable — logging, the
lid-inhibitor gate, restore_keyboards, the failure dump) and the
nomarchy-keyboard-layout helper it calls move out of hyprland.nix into
leaf files (modules/home/display-transition.nix, keyboard-tool.nix),
imported by both hyprland.nix and idle.nix.

This kills the lossy ~22-line mini idle.nix carried under the same binary
name to dodge a circular import. The hypridle wake path (after_sleep /
DPMS on-resume) now runs the real undock — restore_keyboards after a
reload and the evidence dump on enable-failure — instead of a bare
keyword+reload, and the two copies can no longer drift.

Behaviour on the hyprland side is unchanged: the built
nomarchy-display-transition and nomarchy-keyboard-layout have
byte-identical store paths on HEAD vs this change (verbatim extraction).

Verify: all four files parse; home activationPackage + system toplevel
build; checks.docking-ux green (bash -n + safety-feature greps on the
extracted scripts). The tools/monitor-fallback.nix dock harness is red on
main already (the #148 reload-mid-dock assertion — identical failure on
clean HEAD; filed BACKLOG #154), so it could not gate this. The idle
wake-path behaviour change (full undock, incl. dock-intent clearing) is
V3 pending: on-hardware suspend/resume + zero-output rescue queued in
HARDWARE-QUEUE.

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

modules/home/display-transition.nix

@@ -0,0 +1,191 @@
+# The full dock / undock / enable display-transition primitive
+# (nomarchy-display-transition) — the one safety-critical copy. Extracted
+# from hyprland.nix (#150) so hyprland.nix and idle.nix share it instead of
+# idle.nix carrying a lossy mini that lacked logging, the lid-inhibitor
+# gate, restore_keyboards, and the failure dump.
+#
+# One transition primitive for the interactive Dock mode, abrupt undock,
+# and named profiles that disable the internal panel.  Dock is one Hyprland
+# batch: enable the target, move every internal workspace, focus it, then
+# disable the panel.  Undock deliberately enables the panel FIRST, waits
+# for it to become an active target, then restores every workspace.
+#
+#   sync            — nomarchy-state-sync exe (dock-intent writes)
+#   keyboardTool    — nomarchy-keyboard-layout (restore after reload)
+#   displayDumpTool — nomarchy-display-dump (evidence on enable failure)
+{ pkgs, sync, keyboardTool, displayDumpTool }:
+pkgs.writeShellScriptBin "nomarchy-display-transition" ''
+    set -u
+    LOGGER=${pkgs.util-linux}/bin/logger
+    log() { "$LOGGER" -t nomarchy-display-transition -- "$*"; }
+    valid_output() {
+      case "$1" in *[!A-Za-z0-9_.:-]*|"") return 1 ;; *) return 0 ;; esac
+    }
+    workspaces_on() {
+      hyprctl workspaces -j 2>/dev/null \
+        | jq -r --arg m "$1" '.[] | select(.monitor == $m and .id > 0) | .id'
+    }
+    all_workspaces() {
+      hyprctl workspaces -j 2>/dev/null | jq -r '.[] | select(.id > 0) | .id'
+    }
+    lid_inhibitor_held() {
+      ${pkgs.systemd}/bin/systemd-inhibit --list --json=short 2>/dev/null \
+        | ${pkgs.jq}/bin/jq -e 'any(.[]; .what == "handle-lid-switch" and .why == "Safe dock/undock display transition" and .mode == "block")' \
+            >/dev/null
+    }
+    batch_moves() { # stdin workspace ids, $1 target
+      target="$1"; commands=
+      while IFS= read -r ws; do
+        case "$ws" in *[!0-9]*|"") continue ;; esac
+        commands="$commands dispatch moveworkspacetomonitor $ws $target;"
+      done
+      printf '%s' "$commands"
+    }
+    # `monitors` (enabled-only) listing the output is the ONLY proof it is
+    # really on: every path here issues keywords hyprctl answers "ok" to
+    # without acting.  $1 = output, $2 = polls of 0.2s.
+    output_enabled() {
+      tries=0
+      while [ "$tries" -lt "$2" ]; do
+        hyprctl monitors -j 2>/dev/null \
+          | jq -e --arg m "$1" 'any(.[]; .name == $m)' >/dev/null && return 0
+        tries=$((tries+1)); sleep 0.2
+      done
+      return 1
+    }
+    # `hyprctl reload` re-reads the config, and every runtime keyword dies
+    # with it — including the `device[<name>]:kb_layout` the keyboard watcher
+    # applies to an external board.  Measured on hardware 2026-07-14: a bare
+    # reload took a keyboard remembered as `us` straight back to the session's
+    # `gb`, so without this the undock's escalation would silently break the
+    # layout of any keyboard that stays behind when the dock leaves (a
+    # wireless receiver in the laptop; only boards on the dock's own hub are
+    # unaffected, and only because they leave with it).  The remembered
+    # choices live in the in-flake state, so `restore` is authoritative.
+    restore_keyboards() {
+      hyprctl devices -j 2>/dev/null | jq -r '.keyboards[].name' 2>/dev/null \
+        | while IFS= read -r kb; do
+            [ -n "$kb" ] || continue
+            ${keyboardTool}/bin/nomarchy-keyboard-layout restore "$kb" \
+              >/dev/null 2>&1 || true
+          done
+    }
+
+    # Dock mode is an *intent*, and until #142 it lived only in the compositor:
+    # `keyword monitor <internal>, disable` and nothing written down. Any config
+    # reload re-applies the catch-all `monitor=,preferred,auto,1` and re-lights
+    # the panel — which is exactly why `undock` below uses `hyprctl reload` as
+    # its hammer — so every `nomarchy-home` silently performed an undock and the
+    # user re-picked Dock mode by hand.
+    #
+    # So record the intent where every other setting lives (the in-flake state,
+    # menu-writable), and let the watcher re-assert it. `--no-switch`: the
+    # watcher reads this at run time; a rebuild here would be both pointless and
+    # recursive. Failure to write is never fatal — a session that cannot reach
+    # the state file must still dock.
+    set_dock_intent() { # $1 = true|false
+      ${sync} --quiet set settings.display.dockMode "$1" --no-switch \
+        >/dev/null 2>&1 || log "dock-intent=$1 result=state-write-failed"
+    }
+
+    case "''${1:-}" in
+      dock)
+        internal="''${2:-}"; external="''${3:-}"
+        rule="''${4:-$external, preferred, auto, 1}"
+        valid_output "$internal" && valid_output "$external" \
+          || { echo "invalid monitor name" >&2; exit 64; }
+        # Fail closed: disabling the panel without this lock recreates the
+        # exact cable-removal → logind suspend race #100 is fixing.
+        lid_inhibitor_held \
+          || { log "transition=dock internal=$internal external=$external result=no-lid-inhibitor"; exit 1; }
+        moves=$(workspaces_on "$internal" | batch_moves "$external")
+        if hyprctl --batch \
+            "keyword monitor $rule; $moves dispatch focusmonitor $external; keyword monitor $internal, disable" \
+            >/dev/null 2>&1; then
+          set_dock_intent true
+          log "transition=dock internal=$internal external=$external result=ok"
+        else
+          log "transition=dock internal=$internal external=$external result=failed"
+          exit 1
+        fi ;;
+      undock)
+        internal="''${2:-}"
+        valid_output "$internal" || { echo "invalid monitor name" >&2; exit 64; }
+        # Clear the intent *first*: this path runs when the external is already
+        # gone, and if anything below fails the last thing the session needs is
+        # a watcher that keeps trying to dock to a monitor that left.
+        set_dock_intent false
+        # Safety-critical ordering: never remove/move away from an external
+        # before the internal panel is active and can receive workspaces.
+        #
+        # With ZERO enabled outputs — an abrupt undock, the panel already
+        # disabled by the dock — Hyprland 0.55.4 accepts `keyword monitor`
+        # (prints "ok", exits 0) and then never flushes it: the rule is held
+        # until some DRM event arrives, and the panel stays dark.  This is
+        # deterministic, not a race.  Probed on hardware 2026-07-14: the
+        # keyword was inert across 4s and 5s windows in two separate runs,
+        # `dispatch forcerendererreload` did not flush it either, and only
+        # `hyprctl reload` did — in 99ms and 289ms, with the cable out.
+        #
+        # Round 6 read the same symptom as a teardown race and re-issued the
+        # keyword 25 times a poll.  Retrying an inert command cannot work: it
+        # bought 30s of black screen and every `result=ok` in that journal was
+        # really the user plugging the cable back in, whose hotplug flushed
+        # the queued rule and let the next poll take the credit.
+        #
+        # So issue the keyword once — enough whenever another output is still
+        # enabled, e.g. the menu's Dock mode toggle — and escalate to the
+        # reload hammer only when it proves inert.
+        hyprctl keyword monitor "$internal,preferred,auto,1" >/dev/null 2>&1
+        if ! output_enabled "$internal" 5; then
+          log "transition=undock internal=$internal keyword=inert escalate=reload"
+          hyprctl reload >/dev/null 2>&1
+          if ! output_enabled "$internal" 25; then
+            log "transition=undock internal=$internal result=enable-failed"
+            # #127: leave evidence on disk without SSH (TTY or next login).
+            ${displayDumpTool}/bin/nomarchy-display-dump undock-enable-failed \
+              >/dev/null 2>&1 || true
+            exit 1
+          fi
+          # The config's monitor rules own the panel now.  Re-assert the
+          # runtime rule — which flushes normally, an output being enabled
+          # again — so a config that parks the panel off cannot undo the
+          # undock, and give the keyboards back what the reload took.
+          hyprctl keyword monitor "$internal,preferred,auto,1" >/dev/null 2>&1
+          restore_keyboards
+          log "transition=undock internal=$internal enable=via-reload"
+        fi
+        moves=$(all_workspaces | batch_moves "$internal")
+        hyprctl --batch "$moves dispatch focusmonitor $internal" >/dev/null 2>&1 \
+          || { log "transition=undock internal=$internal result=move-failed"; exit 1; }
+        # #127: undock after idle DPMS left the seat black even when the
+        # panel was re-enabled — always light the chain after enable.
+        hyprctl dispatch dpms on >/dev/null 2>&1 || true
+        log "transition=undock internal=$internal result=ok" ;;
+      enable)
+        internal="''${2:-}"
+        valid_output "$internal" || exit 64
+        # Menu ▸ Display ▸ "Screen on". Turning the laptop panel back on *is*
+        # leaving dock mode, and saying so is what stops the watcher from
+        # re-docking the panel out from under the user a second later (#142).
+        # Only the internal clears the intent: lighting some third monitor is
+        # not a statement about the lid.
+        case "$internal" in
+          eDP*|LVDS*|DSI*) set_dock_intent false ;;
+        esac
+        # Reachable only from the menu, i.e. with a screen already on, so the
+        # keyword flushes and no reload escalation is needed — but still make
+        # `monitors` the proof, or the menu's "back on" notification cheers
+        # for a keyword hyprctl merely said "ok" to.
+        hyprctl keyword monitor "$internal,preferred,auto,1" >/dev/null 2>&1
+        if output_enabled "$internal" 10; then
+          hyprctl dispatch dpms on >/dev/null 2>&1 || true
+          true
+        else
+          false
+        fi ;;
+      *)
+        echo "usage: nomarchy-display-transition [dock <internal> <external> [external-rule]|undock <internal>|enable <internal>]" >&2
+        exit 64 ;;
+    esac
+  ''