canbus: Discord alert when the water-heater DSI fault trips

New Pi package (repo copy canbus/ha/dsi_fault_alert.yaml): when the CAN
node's DSI-lockout binary sensor holds 'on' for 10s, fire the server-
alerts Discord webhook (@here, appropriately rude), with a cleared
message when it recovers. Webhook URL lives in the Pi's HA secrets.yaml
(!secret discord_server_alerts_webhook), not the repo.

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

canbus/HANDOFF.md

@@ -161,5 +161,9 @@ into the YAML as two `binary_sensor`s; nothing left to do here.
 
 - **Water Heater DSI Fault** = node `95` page-3 `b0` bit5 (`0x20`). Healthy heater
   = `0x80` off / `0x81` running; lockout = `0xA0`.
+- **Discord alert wired (2026-06-12):** `canbus/ha/dsi_fault_alert.yaml` (on the
+  Pi as `packages/dsi_fault_alert.yaml`) pings the server-alerts channel via
+  webhook (`!secret discord_server_alerts_webhook`, same one Gatus uses) when
+  the fault latches for 10 s, plus a cleared message. Test-fired OK.
 - **OneControl System Fault** = page-0 `b0` bit0 (`0x01`), a bus-wide
   "fault exists somewhere" flag (read from node `95`'s page 0 in the lambda).

canbus/ha/dsi_fault_alert.yaml

@@ -0,0 +1,58 @@
+# Water-heater DSI fault → Discord ping in the server-alerts channel.
+#
+# The CAN node decodes the heater's DSI lockout (node 95 page-3 b0 bit5 —
+# see canbus/README.md); when the burner fails to light (usually an empty
+# propane tank) the module latches the fault and this fires the webhook.
+#
+# Deploy to Pi: /config/packages/dsi_fault_alert.yaml
+# Repo copy:    canbus/ha/dsi_fault_alert.yaml
+# Secret:       discord_server_alerts_webhook in the Pi's /config/secrets.yaml
+#               (same webhook Gatus uses for the alerts channel)
+
+rest_command:
+  discord_server_alerts:
+    url: !secret discord_server_alerts_webhook
+    method: POST
+    content_type: "application/json; charset=utf-8"
+    payload: >-
+      {"username": "Camper OneControl",
+       "content": {{ message | tojson }},
+       "allowed_mentions": {"parse": ["everyone"]}}
+
+automation:
+  - id: camper_dsi_fault_discord
+    alias: "Camper: DSI fault → Discord"
+    description: >-
+      10s 'for' debounces a single glitched broadcast frame; a real lockout
+      is latched by the module so it easily survives the wait.
+    triggers:
+      - trigger: state
+        entity_id: binary_sensor.onecontrol_can_water_heater_dsi_fault
+        to: "on"
+        for: "00:00:10"
+    actions:
+      - action: rest_command.discord_server_alerts
+        data:
+          message: >-
+            @here 🔥 **WATER HEATER DSI FAULT** — hey dumbass, you're out of
+            propane again. (Or the igniter finally died, but let's be honest,
+            it's the propane.) The heater is in lockout — swap the tank, then
+            cycle the heater off/on to relight.
+    mode: single
+
+  - id: camper_dsi_fault_cleared_discord
+    alias: "Camper: DSI fault cleared → Discord"
+    triggers:
+      - trigger: state
+        entity_id: binary_sensor.onecontrol_can_water_heater_dsi_fault
+        from: "on"
+        to: "off"
+        for: "00:00:10"
+    actions:
+      - action: rest_command.discord_server_alerts
+        data:
+          message: >-
+            ✅ DSI fault cleared — the water heater is lighting again. Crisis
+            averted. Try to remember this feeling next time you eyeball the
+            tank gauge and say "eh, it's fine."
+    mode: single