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>

agent/JOURNAL.md

@@ -17,6 +17,32 @@ Template:
 
 ---
 
+## 2026-07-05 — display profiles slice a (iteration #28, item 15a)
+- **Task:** BACKLOG NEXT#15 slice a, per the #27 design: option +
+  overlay + applier + menu + template example.
+- **Did:** nomarchy.displayProfiles (attrsOf (listOf monitorType));
+  monitor logic extracted to pure modules/home/monitor-rules.nix
+  (rule renderer + 3-layer resolve: profile replaces whole-by-name →
+  resolution picks field-level with the disable-guard → wildcard),
+  hyprland.nix consumes it and gains nomarchy-display-profile
+  (list/active/apply/base; apply = baked hyprctl rules + state write
+  --no-switch, base = clear + hyprctl reload) on PATH only when
+  profiles exist; menu: Display gains a gated "Profiles ›" row + new
+  display-profile mode (●/○ active mark, Base layout row); template
+  example + README row. checks.display-profiles unit-tests resolve
+  (incl. junk-state degradation) — the first HM-eval fixture attempt
+  hit "path not valid" (eval store won't realise writeText/toFile
+  under flake check), hence the pure-function extraction.
+- **Verified:** V0 (check's asserts force at eval); V1 — scratch
+  downstream through lib.mkFlake builds: tool bash -n + correct baked
+  rules (disable, vrr, floats), hyprland.conf shows the exact overlay
+  (wildcard + kept base + disabled panel + profile output), menu bash
+  -n, list/usage smoke. Live switching needs a session+dock → V3.
+- **Pending:** V3 queued. Slices b (hotplug auto-switch) and c
+  (workspace binding) remain in the item.
+- **Next suggestion:** #16 greeter theming, or 15b if momentum on
+  displays is preferred.
+
 ## 2026-07-05 — display-profiles design pass (iteration #27, item 15, no code)
 - **Task:** BACKLOG NEXT#15 — the entry itself demands "design first,
   write the plan into this entry before coding". Backlog-only iteration.