refactor: refactor and fix bug for snappy frame lib

[GrapeBaBa]

Fix the snappy frame issues found by interop.

1. Broken chunk-length maths: upstream’s getChunkSize shifts by <<9 instead of <<8, so lengths are mis-read. Any chunk larger than 511 bytes will decode incorrectly or terminate early.
2. CRC handling is off-spec: the Snappy frame format requires a masked CRC-32C. Their encoder writes the raw CRC via snappy.crc, and the decoder drops it entirely—no masking, no validation. Interop peers will reject our frames, and we wouldn’t catch corrupt payloads.
3. Decoder ignores framing invariants: it never checks the stream identifier and immediately falls back to writing payload bytes, so malformed headers slip through and the caller can’t detect it.

[Copilot]

Pull Request Overview

This PR refactors the Snappy framing implementation to fix critical bugs that prevent proper interoperability with external Snappy frame implementations. The changes address broken chunk-length calculations, incorrect CRC handling, and missing stream identifier validation.

• Fixes chunk length calculation that was using incorrect bit shifts, causing chunks >511 bytes to decode incorrectly
• Implements proper masked CRC-32C validation per Snappy frame specification
• Adds stream identifier validation and proper frame format enforcement

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 3 changed files in this pull request and generated 2 comments.

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[Copilot]

The magic number 8 used for compression threshold calculation should be extracted as a named constant (e.g., compression_ratio_threshold = 8) to clarify its purpose and make it configurable.

[Copilot]

The magic numbers 31 and 251 used for test data generation should be extracted as named constants to clarify their purpose as pseudo-random data generation parameters.

Suggested change

	for (large_data, 0..) |*byte, idx| {
	byte.* = @intCast((idx * 31) % 251);
	const test_data_multiplier = 31;
	const test_data_modulus = 251;
	for (large_data, 0..) |*byte, idx| {
	byte.* = @intCast((idx * test_data_multiplier) % test_data_modulus);