Fix compressed BLE file transfers

bitchatTests/Protocols/BitchatFilePacketTests.swift

@@ -0,0 +1,47 @@
+import XCTest
+@testable import bitchat
+
+final class BitchatFilePacketTests: XCTestCase {
+
+    func testRoundTripPreservesFields() throws {
+        let content = Data((0..<4096).map { UInt8($0 % 251) })
+        let packet = BitchatFilePacket(
+            fileName: "sample.jpg",
+            fileSize: UInt64(content.count),
+            mimeType: "image/jpeg",
+            content: content
+        )
+
+        guard let encoded = packet.encode() else {
+            return XCTFail("Failed to encode file packet")
+        }
+        guard let decoded = BitchatFilePacket.decode(encoded) else {
+            return XCTFail("Failed to decode file packet")
+        }
+
+        XCTAssertEqual(decoded.fileName, packet.fileName)
+        XCTAssertEqual(decoded.fileSize, packet.fileSize)
+        XCTAssertEqual(decoded.mimeType, packet.mimeType)
+        XCTAssertEqual(decoded.content, packet.content)
+    }
+
+    func testDecodeFallsBackToContentSizeWhenFileSizeMissing() throws {
+        let content = Data(repeating: 0x7F, count: 1024)
+        let packet = BitchatFilePacket(
+            fileName: nil,
+            fileSize: nil,
+            mimeType: nil,
+            content: content
+        )
+
+        guard let encoded = packet.encode() else {
+            return XCTFail("Failed to encode file packet")
+        }
+        guard let decoded = BitchatFilePacket.decode(encoded) else {
+            return XCTFail("Failed to decode file packet")
+        }
+
+        XCTAssertEqual(decoded.fileSize, UInt64(content.count))
+        XCTAssertEqual(decoded.content, content)
+    }
+}