Fix Windows test failures due to ArrayPool buffer sizing

[Copilot]

Windows tests failed because ArrayPool<byte>.Shared.Rent() returns buffers larger than requested on Windows but not on Linux. Tests used test.Length (actual rented size) instead of the requested size for reads and comparisons.

Changes

• SharpCompressStreamTest.cs: Changed Read() calls to use explicit size 0x1000 instead of test.Length
• Array comparisons: Use .Take(0x1000) to compare only the requested portion of rented buffers

// Before (fails on Windows when ArrayPool returns larger buffer)
scs.Read(test, 0, test.Length);
Assert.True(data.Skip(0x1000).Take(test.Length).SequenceEqual(test));

// After (works regardless of actual buffer size)
scs.Read(test, 0, 0x1000);
Assert.True(data.Skip(0x1000).Take(0x1000).SequenceEqual(test.Take(0x1000)));

This aligns with ArrayPool contract: rented buffers may be larger than requested and only the specified portion should be used.

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