feat(displays): display profiles — docked/undocked switching (item 15a)

nomarchy.displayProfiles: named layouts for the same outputs, each a
list of nomarchy.monitors-style entries. The active profile lives in
the in-flake state (settings.displayProfile) on the night-light
pattern: nomarchy-display-profile apply <name> fires the baked hyprctl
rules instantly and writes the state with --no-switch; the next rebuild
bakes the profile's entries over nomarchy.monitors whole-by-name.
Monitor-rule composition is extracted to pure monitor-rules.nix
(renderer + 3-layer resolve, incl. a disable-guard so a stale menu
resolution pick can't resurrect a profile-disabled panel, and junk
state degrading to base config instead of an eval error) — because a
writeText/toFile state fixture is unreadable at flake-check eval time,
the new checks.display-profiles unit-tests the pure function directly.
Menu: System › Display gains a self-gated "Profiles ›" row (●/○ active
mark, Base layout to clear); commented template example + README row.

Verified: V0 (flake check, forcing the new check's asserts); V1 — a
scratch downstream through lib.mkFlake builds: the generated tool
passes bash -n with correct rules (disable/vrr/float scale), the baked
hyprland.conf shows the exact expected overlay, the menu renders, and
list/usage smoke-test clean. Remains: V3 live switching on a dock
(HARDWARE-QUEUE). Slices b (hotplug auto-switch) + c (workspace
binding) stay in item 15.

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

modules/home/monitor-rules.nix

@@ -0,0 +1,67 @@
+# Pure monitor-rule composition, split out of hyprland.nix so
+# checks.display-profiles can exercise the overlay semantics directly —
+# no Home Manager evaluation, no state-file fixture.
+{ lib }:
+
+rec {
+  # Skeleton for an entry built outside the option type (mirrors the
+  # monitorType defaults in options.nix).
+  defaults = {
+    resolution = "preferred"; position = "auto"; scale = 1;
+    transform = null; mirror = null; bitdepth = null; vrr = null; extra = "";
+  };
+
+  # An entry -> a Hyprland `monitor` rule. Unset optional fields are
+  # omitted; `resolution = "disable"` collapses to the short form.
+  rule = m:
+    if m.resolution == "disable" then "${m.name}, disable"
+    else lib.concatStringsSep ", " (
+      [ m.name m.resolution (toString m.position) (toString m.scale) ]
+      ++ lib.optionals (m.transform != null) [ "transform" (toString m.transform) ]
+      ++ lib.optionals (m.mirror != null) [ "mirror" m.mirror ]
+      ++ lib.optionals (m.bitdepth != null) [ "bitdepth" (toString m.bitdepth) ]
+      ++ lib.optionals (m.vrr != null) [ "vrr" (toString m.vrr) ]
+      ++ lib.optional (m.extra != "") m.extra
+    );
+
+  # The full overlay, three layers:
+  #
+  #  1. base (nomarchy.monitors) with the ACTIVE display profile's entries
+  #     (settings.displayProfile naming a nomarchy.displayProfiles key)
+  #     replacing base entries WHOLE, by name — a profile entry is a
+  #     complete statement about that output. Outputs a profile doesn't
+  #     name keep their base rules; a cleared/unknown/non-string value
+  #     ("" after `nomarchy-display-profile base`, or hand-edited junk —
+  #     the validator only warns) means base config only.
+  #
+  #  2. Menu-remembered per-output resolutions (settings.monitors:
+  #     output-name -> "WxH@R", written instantly by the Display menu)
+  #     overlaid field-level by name: a declared output keeps its
+  #     position/scale/etc and only its resolution changes; an output
+  #     covered solely by the `,preferred,auto,1` wildcard (e.g. the
+  #     laptop's built-in panel) becomes a new rule with default
+  #     position/scale. The menu pick wins over a hand-set resolution
+  #     (it's the explicit live action) — EXCEPT onto disabled entries: a
+  #     stale pick, made while the output was enabled, must not resurrect
+  #     a panel the active profile (or the base config) disables.
+  #
+  #  3. Anything still uncovered falls to the wildcard (hyprland.nix
+  #     prepends it).
+  resolve = { base, profiles, active, resOverrides }:
+    let
+      activeName = if builtins.isString active then active else "";
+      profileEntries = profiles.${activeName} or [ ];
+      profileNames = map (m: m.name) profileEntries;
+      baseMonitors =
+        lib.filter (m: ! lib.elem m.name profileNames) base
+        ++ profileEntries;
+      declaredNames = map (m: m.name) baseMonitors;
+    in
+    map (m: if resOverrides ? ${m.name} && m.resolution != "disable"
+            then m // { resolution = resOverrides.${m.name}; }
+            else m)
+        baseMonitors
+    ++ lib.mapAttrsToList
+         (name: res: defaults // { inherit name; resolution = res; })
+         (lib.filterAttrs (name: _: ! lib.elem name declaredNames) resOverrides);
+}