Ship a low-battery-warning bread module by default

A zero-config bread module (auto-discovered) that fires a critical
notification once when the battery runs low and resets on AC. No-op on
desktops. Demonstrates the bread automation layer out of the box.

iso/airootfs/etc/skel/.config/bread/modules/low-battery-warning.lua

@@ -0,0 +1,26 @@
+-- low-battery-warning — notify once when the battery runs low (zero-config).
+-- Shipped active in BOS; auto-discovered by breadd. Safe on desktops too
+-- (simply never fires without a battery).
+
+local M = bread.module({ name = "low-battery-warning", version = "1.0.0" })
+
+local warned = false
+
+function M.on_load()
+    bread.on("bread.power.battery.low", function(event)
+        if warned then return end
+        warned = true
+        local pct = event.data.battery_percent or "?"
+        bread.notify("Battery low (" .. pct .. "%). Plug in soon.", {
+            urgency = "critical",
+            title   = "Battery",
+            timeout = 10000,
+        })
+    end)
+
+    bread.on("bread.power.ac.connected", function()
+        warned = false
+    end)
+end
+
+return M