docs(agent): file #118 — smartd fails with no SMART device, reddening the health icon

Bernardo tested the live ISO and saw a smartd error on the Waybar doctor
module. Filed with the cause rather than the symptom: reproduced headlessly in
a scratch runNixOSTest whose node's only config is services.smartd.enable =
true — the same block default.nix:166 mkDefaults on for every machine.

  smartd: In the system's table of devices NO devices found to scan
  smartd: Unable to monitor any SMART enabled devices. Exiting.
  smartd.service: Main process exited, code=exited, status=17/n/a

Everything downstream is working correctly: systemctl --failed lists
smartd.service, so the doctor's generic failed-unit check reports it and
#custom-doctor goes @bad. The doctor is telling the truth — smartd is what
needs fixing.

Scope is wider than the live ISO, which is why it sits in NOW with the other
live findings rather than as a live-only nit: smartd mkDefaults true on
`nomarchy` too, and QEMU virtio disks expose no SMART, so a plain VM install
boots to a red health icon out of the box. Every V2 QEMU run has been showing
this.

The fix direction is the distro's own self-gate convention: `smartctl --scan`
prints nothing on such a machine, so an ExecCondition leaves the unit inactive
instead of failed and real SMART failures still surface. Recorded explicitly
that SuccessExitStatus = 17 is the wrong fix — it would also swallow smartd
dying on a machine that does have drives, which is the reason the daemon
exists.

V0: nix flake check --no-build passes. Backlog only — no fix attempted here.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agent/BACKLOG.md

@@ -30,6 +30,48 @@ These are separate queue items from one real install/session pass. Preserve
 that separation when fixing them: the installer blocker, unclear installer
 copy, and post-install desktop failures have different verification paths.
 
+### 118. smartd fails where no drive has SMART, so the health icon greets you red
+
+Bernardo, live ISO 2026-07-14: the Waybar doctor module shows a smartd error.
+
+**Root cause, reproduced headlessly 2026-07-14** (scratch `runNixOSTest`, a
+node whose only config is `services.smartd.enable = true` — the same block
+`modules/nixos/default.nix:166` mkDefaults ON for every machine):
+
+    smartd[567]: In the system's table of devices NO devices found to scan
+    smartd[567]: Unable to monitor any SMART enabled devices. Exiting.
+    smartd.service: Main process exited, code=exited, status=17/n/a
+    Status: "No devices to monitor"
+
+`smartctl --scan` prints **nothing** on such a machine — which is both the
+cause and the ready-made gate. The rest of the chain is each part working
+correctly: `systemctl --failed` lists `smartd.service`, so nomarchy-doctor's
+generic failed-unit check (`nomarchy-doctor.sh:24-28`) reports "failed system
+unit(s): smartd.service", and Waybar's `#custom-doctor` goes `@bad`. **Fix
+smartd, not the doctor** — the doctor is telling the truth about a unit that
+genuinely failed.
+
+**Scope is wider than the live ISO** (which is why it's here and not filed as
+a live-only nit): `services.smartd.enable` mkDefaults true on `nomarchy` as
+well as `nomarchy-live`, and QEMU virtio disks expose no SMART — so a plain
+VM install boots to a red health icon out of the box, as does a live USB whose
+stick has no SMART. Every V2 QEMU run has been showing this.
+
+Fix direction: **self-gate on the hardware**, the convention the rest of the
+distro follows (`ExecCondition`, like the night-light; "each half self-gates
+on its hardware"). A condition that runs `smartctl --scan` and skips the unit
+when it finds nothing leaves the unit *inactive* rather than *failed*, so real
+SMART failures on real drives still surface. Do **not** paper over it with
+`SuccessExitStatus = 17` — that also swallows the case where smartd dies on a
+machine that does have drives, which is the whole reason the daemon is here.
+
+Pass = on a machine with no SMART-capable device the unit is inactive (not
+failed), `systemctl --failed` is empty and the doctor is green; on a machine
+with one, smartd runs as it does today; a permanent `checks.*` covers both
+halves (the scratch repro above is most of it — the no-SMART node exists, the
+with-SMART node needs a QEMU disk that answers SMART, or the gate script
+tested directly against a stubbed `smartctl`).
+
 ### 94. Live ISO/install: no default browser observed
 
 **Progress 2026-07-13:** installed path VERIFIED at V1 — the exact HM