Reject oversized blocks_by_range requests and add tests

[devylongs]

Motivation

• Ensure peers cannot send compressed range requests larger than MaxCompressedPayloadSize to avoid resource exhaustion or unexpected behavior.

Description

• Add a readRangeRequest helper that reads up to MaxCompressedPayloadSize+1 bytes and returns a specific error when the compressed request exceeds MaxCompressedPayloadSize.
• Introduce errRangeRequestTooLarge and update handleBlocksByRangeRequest to use readRangeRequest and respond with RespInvalidRequest and message "request too large" when the helper reports an oversized request.
• Add unit tests and a test stream shim: TestReadRangeRequestSizeLimit validates reading at and above the limit, and TestBlocksByRangeRejectsOversizedRequest ensures oversized requests are rejected and block lookup is not invoked.

Testing

• Ran unit tests in the internal/p2p package including TestReadRangeRequestSizeLimit and TestBlocksByRangeRejectsOversizedRequest.
• All added and existing tests in the package passed.

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Codex Task

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-24T17:56:12.306397Z	a48aaf2	PR opened
🔒 Security Review	✅ Completed 2026-09-24T17:56:51.504995Z	a48aaf2	PR opened

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