Add flaps: flappable tag, flap lever on the control node, flap physics (0.4.0)

Shift-right-click a block in improved_aerodynamics:flappable to make it a flap.
G/H step the node's flap lever UP/TAKEOFF/LANDING; flaps slew to the configured
angle, add lift and drag and raise the stall angle, and retract above a max speed.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YVREx3uo7nz1FEhzveWTUh

src/main/java/dev/lumareth/improvedAerodynamics/network/FlapPacket.java

@@ -0,0 +1,33 @@
+package dev.lumareth.improvedAerodynamics.network;
+
+import dev.lumareth.improvedAerodynamics.flight.FlapControl;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraftforge.fml.ModList;
+import net.minecraftforge.network.NetworkEvent;
+
+import java.util.function.Supplier;
+
+/** Sent when a pilot moves the flap lever: more flaps (true) or fewer. */
+public final class FlapPacket {
+    private final boolean extend;
+
+    public FlapPacket(boolean extend) {
+        this.extend = extend;
+    }
+
+    public void encode(FriendlyByteBuf buffer) {
+        buffer.writeBoolean(extend);
+    }
+
+    public static FlapPacket decode(FriendlyByteBuf buffer) {
+        return new FlapPacket(buffer.readBoolean());
+    }
+
+    public void handle(Supplier<NetworkEvent.Context> context) {
+        ServerPlayer player = context.get().getSender();
+        if (player != null && ModList.get().isLoaded("valkyrien_warium")) {
+            FlapControl.step(player, extend ? 1 : -1);
+        }
+    }
+}