fix snappy frame multi chunks and refactor

[GrapeBaBa]

• Improve req/resp snappy framing to compute total frame size from chunk headers, validate chunk types/lengths, and handle multi‑chunk frames based on the declared uncompressed
  length.
• Thread the declared uncompressed length through inbound/outbound codecs and Zig RPC handling to verify decoded payload size matches the declaration and reject mismatches.
• Remove the heuristic compressed‑size overhead check in favor of strict framing validation; minor lint cleanup.

[Copilot]

Pull request overview

This PR fixes snappy frame handling to properly support multi-chunk frames and refactors the validation logic for improved precision and security.

Changes:

• Implemented multi-chunk snappy frame parsing with proper accumulation of uncompressed lengths across chunks
• Replaced heuristic frame size validation with precise calculation using snap::raw::max_compress_len
• Added defense-in-depth validation by checking decompressed length matches declared length on the Zig side

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
rust/libp2p-glue/src/req_resp/varint.rs	Refactored calculate_snappy_frame_size to handle multi-chunk frames, added max_framed_len helper, improved validation with overflow checks
rust/libp2p-glue/src/req_resp/outbound_protocol.rs	Updated calls to calculate_snappy_frame_size with new parameter, removed heuristic validation
rust/libp2p-glue/src/req_resp/inbound_protocol.rs	Updated calls to calculate_snappy_frame_size with new parameter, removed heuristic validation
pkgs/network/src/ethlibp2p.zig	Enhanced frame parsing to return declared length, added validation that decompressed length matches declared length

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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[g11tech]

seems already tested against ream interop