Ship the 0.8.0 first-hour and campaign milestone

Add the campaign shell, pause-safe checkpoint resume, post-shift campaign
continue, confirmed campaign reset, difficulty presets, searchable Help,
content-matrix validation, recovery events, contextual dialogue, policy/debrief
context and eligible-event previews. Extend persistence with atomic separate
files and add campaign/checkpoint/tutorial smokes. Headless 247/247, Python
94/94, tutorial/campaign/session/scenario smokes green.

src/core/radio_system.gd

@@ -123,6 +123,23 @@ func tick(delta: float) -> void:
 		if event_bus:
 			event_bus.responder_arrived.emit(call)
 
+func snapshot() -> Dictionary:
+	return {
+		"battery": battery,
+		"emergency_cooldown_remaining": emergency_cooldown_remaining,
+		"accepting_calls": accepting_calls,
+		"pending_calls": pending_calls.duplicate(true),
+	}
+
+func restore(data: Dictionary) -> void:
+	battery = clampf(float(data.get("battery", 100.0)), 0.0, max_battery)
+	emergency_cooldown_remaining = maxf(0.0, float(data.get("emergency_cooldown_remaining", 0.0)))
+	accepting_calls = bool(data.get("accepting_calls", true))
+	pending_calls.clear()
+	for call in data.get("pending_calls", []):
+		if call is Dictionary:
+			pending_calls.append((call as Dictionary).duplicate(true))
+
 ## Determine the responder's resolution outcome for a call. The responder
 ## commands, restrains, evacuates, or arrests based on the reported danger
 ## level and whether a weapon was seen (PLAN.md: Level 5 Emergency Response).