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/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