Fix Cadente chunked response framing with non-zero offsets

[CypherPotato]

Motivation

• Repair a bug in Cadente where chunked responses declared an incorrect chunk size (using count - offset) and could emit the terminal chunk on empty writes, which can corrupt HTTP/1.1 chunk framing and lead to response desynchronization.

Description

• Update cadente/Sisk.Cadente/Streams/HttpChunkedWriteStream.cs so Write(byte[] buffer, int offset, int count) uses count for the chunk-size header and treats count == 0 as a no-op, while leaving the terminal 0\r\n\r\n emission in Dispose intact.

Testing

• Ran dotnet test tests/Sisk.Core/tests.csproj --no-restore which completed successfully.
• Running dotnet test from the repo root was not applicable because there is no solution/project file at /workspace/core, producing an MSBUILD error.

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Codex Task