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.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"strings"
+	"sync"
+	"time"
+)
+
+const batteryCacheSeconds = 15
+
+type BatteryProbe func() (bool, error)
+
+type batteryWatch struct {
+	mu      sync.Mutex
+	probe   BatteryProbe
+	now     func() time.Time
+	debugf  func(format string, args ...any)
+	checked time.Time
+	value   bool
+	warned  bool
+}
+
+func newBatteryWatch(probe BatteryProbe, now func() time.Time) *batteryWatch {
+	return &batteryWatch{probe: probe, now: now}
+}
+
+func (w *batteryWatch) OnBattery() bool {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+	moment := w.now()
+	if !w.checked.IsZero() && moment.Sub(w.checked) < time.Duration(batteryCacheSeconds)*time.Second {
+		return w.value
+	}
+	w.checked = moment
+	value, err := w.probe()
+	if err != nil {
+		value = false
+		if !w.warned && w.debugf != nil {
+			w.debugf("battery state unknown, treating as mains power: %v", err)
+		}
+		w.warned = true
+	}
+	w.value = value
+	return value
+}
+
+func parsePmset(text string) bool {
+	return strings.Contains(text, "Now drawing from 'Battery Power'")
+}
+
+func windowsOnBattery(acLine, batteryFlag byte) bool {
+	return acLine == 0 && batteryFlag != 128 && batteryFlag != 255
+}