fix(network): correct dest inversion in newPacket(nbt) and null packet size (BUG-058, BUG-059)

[ximaks00-hue]

Summary

Two regressions in Network.scala affecting packet routing and size calculation.

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BUG-058 — newPacket(nbt) inverts dest key check

File: src/main/scala/li/cil/oc/server/network/Network.scala:567-569

Root cause: The condition loading the destination field from NBT is inverted:

// CE (broken)
val destination =
  if (nbt.contains("dest")) null      // "dest" present → null (broadcast!)
  else nbt.getString("dest")          // "dest" absent  → "" (broadcast too)

Save side (line 727) correctly writes "dest" only when destination != null && !destination.isEmpty. So:

• Targeted packet saved with dest = "node-abc" → NBT contains key "dest"
• On load: nbt.contains("dest") → true → destination = null → packet becomes broadcast

Impact: Any targeted modem packet (linked card, relay with unicast) saved in a hub/switch queue is silently converted to a broadcast after world reload. Routing breaks for all targeted transmissions that survive a reload cycle.

Note: This bug is identical in Original 1.12.2 (if (nbt.hasKey("dest")) null else getString). It is not a CE regression per se, but the CE code inherits it — correcting it here brings CE ahead of Original.

Fix: Swap the branches:

val destination =
  if (nbt.contains("dest")) nbt.getString("dest")
  else null

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BUG-059 — Packet.size counts null/None/unit as 4 bytes instead of 1

File: src/main/scala/li/cil/oc/server/network/Network.scala:709

Root cause:

// CE (broken)
case null | ResultWrapper.unit | None => 4
// Original
case null | Unit | None => 1

In OC's packet size calculation, a null/None/unit value represents an empty/void slot. Original counted it as 1 byte. CE counts it as 4 bytes — a 4x inflation for void slots.

Impact:

• Packets with many sparse null / None values hit maxNetworkPacketSize ~4x sooner
• Relay/linked card energy cost calculation (based on packet size) is inflated
• Packets that Original 1.12 would accept are rejected by CE

Fix: => 1 (matches Original).

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Verification

• BUG-058: save writes "dest" when targeted → contains is true on load → inverted condition assigns null → routing bug confirmed.
• BUG-059: 10 null values → CE size 40 bytes; Original 10 bytes. At maxNetworkPacketSize = 8192, CE rejects packets that are mostly sparse data.

Test plan

• Send targeted modem message, save/reload world, verify packet delivered to correct recipient (not broadcast)
• Send packet with null slots across relay — verify energy cost matches expected

[akki697222]

This is a complex network change, so we'll wait for testing.