CBOR store: fall back to ignore for non-binary tagged items

[ameliabarnabyhub]

Fixes #5316 (part 1)

cbor_tag_handler_t::store assumed every tagged item is a byte string. Tagged maps, arrays, and other non-binary values therefore failed with parse_error.113 even though ignore accepted the same input (notably CBOR self-describe tag 55799).

When the tagged item is not a binary head byte, fall back to ignore parsing instead of forcing binary decoding. Binary tags still store the subtype as before.

Does not change behavior for tag numbers 6–20 over binary strings (part 2 of #5316).

[github-actions]

🔴 Amalgamation check failed! 🔴

The source code has not been amalgamated and/or formatted correctly.

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[nlohmann]

Found two correctness issues while reviewing this PR:

1. single_include/nlohmann/json.hpp has diverged from include/ (most severe — likely root cause of the CI failures)

The amalgamation commit adds new logic (throw_on_discarded(), assert_msgpack_size(), discarded values now throwing type_error.318 instead of producing empty output) that never landed in include/nlohmann/detail/output/binary_writer.hpp. That header still has the old break;/JSON_ASSERT(false) paths — confirmed against develop and against this PR's diff, which only touches binary_reader.hpp, single_include/json.hpp, and tests/src/unit-cbor.cpp, never binary_writer.hpp.

Since the test suite compiles against include/, the updated discarded-value tests in tests/src/unit-cbor.cpp (expecting CHECK_THROWS_WITH_AS(...type_error.318...)) can't pass. This lines up with essentially every CI check failing on this PR, including ci_test_amalgamation.

2. The CBOR fix itself has a nested-tag regression

In include/nlohmann/detail/input/binary_reader.hpp (~line 904), the fallback for a non-binary tagged item under store mode hardcodes:

return parse_cbor_internal(false, cbor_tag_handler_t::ignore);

instead of propagating the enclosing tag_handler (which is store here). So tag(100) -> [tag(80) -> h'01'] parsed under store mode loses the inner tag's subtype, because everything inside the non-binary wrapper now gets parsed with ignore instead of store. Passing tag_handler through instead of the literal ignore should fix this without changing the intended behavior for the top-level non-binary tag.

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Posted by Claude Code on behalf of @nlohmann.