feat(power): clamshell — ignore lid suspend when docked (#86)

Explicit HandleLidSwitchDocked=ignore under services.logind so closing
the lid with an external display connected does not suspend. Undocked
lid path left to upstream defaults. checks.clamshell-logind asserts the
baked logind.conf and active logind; real multi-monitor lid V3 queued.

Verified: V2 — flake check --no-build; checks.clamshell-logind green.
V3 pending: HARDWARE-QUEUE #86 lid+external on a laptop.

agent/BACKLOG.md

@@ -55,13 +55,6 @@ runtime-computed `resume_offset` into the boot cmdline, and the dev box runs
 exactly this layout (`/proc/cmdline` verified) but isn't Nomarchy. Steps in
 HARDWARE-QUEUE. Close #76 on PASS.
 
-### 86. Clamshell dock: lid + external monitor (`VISION § C`)
-Lid closed with external monitor connected must not suspend
-(`logind` `lidSwitchDocked` / `ExternalPower` audit + display-profile
-interplay); wake behaves. Display profiles + auto-switch already exist —
-this is the lid/suspend edge case. VM where possible; residual V3 on
-real dock hardware.
-
 ### 87. Dock audio sink follows plug/unplug (`VISION § C`)
 Default audio sink: dock sink on plug, internal on unplug (WirePlumber
 policy or udev hook). Complements #86; can ship independently.
@@ -118,8 +111,8 @@ high-ROI, etc.) live in the journal + ROADMAP — not here.*
   2026-07-10). Keep #59 commented install guidance; no
   `nomarchy.hardware.nvidia.*` until a hybrid maintainer + queue.
 
-_(#80–#83 + #85 shipped 2026-07-11. #84 split → **NEXT #86–#87** dock
-  clamshell + dock audio.)_
+_(#80–#83 + #85–#86 shipped 2026-07-11. Remaining dock slice: **#87**
+  dock audio. #86 V3 clamshell on real external display → HARDWARE-QUEUE.)_
 
 ### v1.0 pointer
 

agent/HARDWARE-QUEUE.md

@@ -11,6 +11,14 @@ the **T14s** (webcam case).
 
 ## Any machine (dev box is fine)
 
+- [ ] **#86 clamshell lid + external display** — V2 asserts
+      `HandleLidSwitchDocked=ignore` in logind.conf. On a laptop with a
+      real external monitor: open a session, plug external, close lid —
+      machine must **stay awake** (no suspend); external panel remains
+      usable (or wakes with keyboard if DPMS). Unplug external, close lid
+      — should suspend as usual. Optional: with a docked display-profile
+      (`eDP-1` disable), confirm clamshell layout still looks right after
+      lid close. Pass = no surprise suspend when docked.
 - [ ] **#55 fingerprint enroll on real reader** — with
       `nomarchy.hardware.fingerprint.enable` and a physical reader: System ›
       Fingerprint › Enroll a finger; List shows it; Verify succeeds; optional

agent/JOURNAL.md

@@ -19,6 +19,18 @@ Template:
 
 ---
 
+## 2026-07-11 — #86 clamshell HandleLidSwitchDocked
+- **Task:** NEXT #86 — lid closed + external monitor must not suspend.
+- **Did:** Explicit `HandleLidSwitchDocked=ignore` in
+  `modules/nixos/power.nix` (logind settings.Login). Undocked lid
+  behaviour unchanged. idle.nix comment corrected. `checks.clamshell-logind`
+  asserts conf + active logind. V3 steps in HARDWARE-QUEUE. Closed #86.
+- **Verified:** **V2** — `nix flake check --no-build`;
+  `checks.clamshell-logind` green (`HandleLidSwitchDocked=ignore` +
+  logind active).
+- **Pending:** V3 real lid+external on laptop (HARDWARE-QUEUE).
+- **Next suggestion:** #87 dock audio sink follow.
+
 ## 2026-07-11 — #85 hardware hall of fame + split #84
 - **Task:** NEXT #85 docs hall of fame; #84 was `[big]` → split.
 - **Did:** HARDWARE.md §9 install-tested table (T14s Gen 4 AMD, Latitude