[armadavalor]

After the NetDataReader rework, the Get* methods call EnsureAvailable, but the Peek* ones do not:

• PeekUnmanaged<T> (so PeekInt, PeekLong, etc.) reads sizeof(T) bytes with Unsafe.ReadUnaligned / a raw pointer. On a 2-byte buffer, PeekInt() reads past the end of the array instead of throwing.
• PeekByte, PeekString and PeekString(int) only check against the array length, not _dataSize. A reader over a NetDataWriter whose backing array is larger than the data returns garbage. For example, a truncated string returns a run of null characters.
• In the UNITY_ANDROID branch, PeekUnmanaged uses size, which is never declared. That branch fails with CS0103. I checked this by compiling with UNITY_ANDROID defined and a stub UnsafeUtility.

The fix adds EnsureAvailable to PeekByte, PeekUnmanaged (which also declares size) and both PeekString overloads. Peeking past the end now throws InvalidOperationException, the same as the matching Get* call.

There are two new tests in ReaderWriterSimpleDataTest. I only have the .NET 7 SDK, so I could not run the net8/net9 test project. I built the library for netstandard2.1 and ran the same assertions from a net7 console. Before the fix, 7 assertions fail; after it, all pass.