Fix CouponList deserialization count validation bug

[jihuayu]

This fixes a CouponList deserialization bug where LIST-mode serialized data could declare a coupon count larger than the fixed LIST capacity.

The change validates the declared LIST count before reading coupon data, and applies the check to both byte-array and stream deserialization paths.

Tests

• cmake --build build/Release --target hll_test
• ./build/Release/hll/test/hll_test
• ctest --test-dir build/Release -R hll_test --output-on-failure
• ctest --test-dir build/ASan -R hll_test --output-on-failure

cc @tisonkun

[tisonkun]

LGTM. Thanks for your contribution!

[Copilot]

Pull request overview

This PR tightens CouponList (LIST-mode) deserialization by validating the declared coupon count against the fixed LIST backing-array capacity, preventing malformed serialized data from causing unsafe reads/writes during deserialization. It also adds regression tests covering both byte-array and stream deserialization entry points.

Changes:

• Add LIST coupon-count capacity validation in CouponList::newList() for both byte-array and stream paths.
• Add new unit tests that mutate serialized bytes/streams to declare an oversized LIST coupon count and assert std::invalid_argument.

Reviewed changes

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

File	Description
hll/test/CouponListTest.cpp	Adds regression tests for malformed LIST coupon-count handling in bytes and stream deserialization.
hll/include/CouponList-internal.hpp	Adds LIST coupon-count validation during deserialization (bytes + stream).

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[Copilot]

Pull request overview

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

[jihuayu]

Hi @tisonkun. Following Copilot's suggestion, I reject cases where couponCount >= listCapacity, and updated the test cases to cover this scenario.

[leerho]

@jihuayu , @tisonkun
Thank you both for helping me close this!