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/options.nix

@@ -237,6 +237,31 @@ in
       '';
     };
 
+    displayProfiles = lib.mkOption {
+      type = lib.types.attrsOf (lib.types.listOf monitorType);
+      default = { };
+      example = lib.literalExpression ''
+        {
+          docked = [
+            { name = "eDP-1"; resolution = "disable"; }
+            { name = "DP-3"; position = "0x0"; }
+            { name = "DP-4"; position = "auto-right"; }
+          ];
+          undocked = [ { name = "eDP-1"; position = "0x0"; } ];
+        }
+      '';
+      description = ''
+        Named display layouts for the same outputs (docked, undocked, …),
+        each a list of nomarchy.monitors-style entries. Switch from the menu
+        (System › Display › Profiles) or `nomarchy-display-profile apply
+        <name>`: the profile's rules apply instantly via hyprctl and the
+        choice persists in the in-flake state (settings.displayProfile), so
+        the next rebuild bakes the active profile's entries over
+        nomarchy.monitors by name. Outputs a profile doesn't name keep
+        their base rules.
+      '';
+    };
+
     # ── Component toggles ──────────────────────────────────────────
     hyprland.enable = lib.mkEnableOption "Nomarchy's Hyprland configuration" // { default = true; };
     waybar.enable = lib.mkEnableOption "Nomarchy's Waybar configuration" // { default = true; };