Code Farm: per-plot auto-replant pause and crop-lock check; community sync and node work

Continuous Delivery could never be turned off once a crop was planted. Add a
one-shot per-plot "stop after harvest" flag (POST /game/plot/stop, Devii tool
game_plot_stop, game_plots.stop_after_harvest), cleared by the next plant,
autoreplant claim or Refactor. Autoreplant now also respects crop locks through
the shared _crop_lock predicate. Plan and measurements in happyplanting.md.

Also includes the pending community sync, node network and related work in the
tree; the full suite passed (4999) with all of it.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

nodes/client/battery_linux.go

@@ -0,0 +1,53 @@
+//go:build linux
+
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const powerSupplyRoot = "/sys/class/power_supply"
+
+func systemBattery() (bool, error) {
+	return sysfsOnBattery(powerSupplyRoot)
+}
+
+func readSupplyField(dir, name string) string {
+	data, err := os.ReadFile(filepath.Join(dir, name))
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(string(data))
+}
+
+func isMainsType(kind string) bool {
+	return kind == "Mains" || kind == "ADP" || strings.HasPrefix(kind, "USB")
+}
+
+func sysfsOnBattery(root string) (bool, error) {
+	entries, err := os.ReadDir(root)
+	if err != nil {
+		return false, err
+	}
+	discharging := false
+	for _, entry := range entries {
+		dir := filepath.Join(root, entry.Name())
+		if readSupplyField(dir, "scope") == "Device" {
+			continue
+		}
+		kind := readSupplyField(dir, "type")
+		switch {
+		case kind == "Battery":
+			if readSupplyField(dir, "status") == "Discharging" {
+				discharging = true
+			}
+		case isMainsType(kind):
+			if readSupplyField(dir, "online") == "1" {
+				return false, nil
+			}
+		}
+	}
+	return discharging, nil
+}