HAOS: System monitoring dashboard + smartmon local addon (SMART via full_access)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/CHANGELOG.md

@@ -3,6 +3,16 @@
 **Purpose:** Major infrastructure events only. Minor changes are in git commit messages.
 
 ---
+## 2026-08-04
+
+### HAOS System monitoring dashboard (CPU/RAM/SSD/temps)
+- **[HA]** New `system-dashboard` (YAML): CPU load/temp gauges, per-core + board temp graphs (command_line sensors reading hwmon), RAM/swap gauges, disk usage, SMART panel, network throughput. System Monitor integration added (13 entities enabled via registry).
+- **[HA]** Local add-on **smartmon v1.0.4** (`/addons/smartmon/`, alpine+smartmontools): loops `smartctl -d sat -s on -H -A -i -j /dev/sda > /share/smart.json` every 5 min; `full_access: true` + `apparmor: false` required (Supervisor bind-mounts /dev but adds no device cgroup rule for block devices — `devices:` list alone gives EPERM). SSD (Samsung MZMTD128HAFV, Lenovo OEM) shipped with SMART disabled → enabled via `-s on`. Baseline: health OK, 41°C, 36 544 POH, wear 92%.
+- **[NOTE]** Fan monitoring/control on HAOS is **impossible**: kernel 6.18.39-haos ships no Super I/O hwmon modules (nct6775/it87/…), no pwm nodes. BIOS-only.
+- **[NOTE]** Local add-on gotchas: no default `BUILD_FROM` (use explicit FROM), config changes need version bump + `/store/addons/<slug>/update`, failed rebuild deletes the image, transient DNS fixed with `ha dns restart`.
+
+---
+
 ## 2026-07-30
 
 ### Roborock: single card + Browser Mod popup (living view redesign)