Remove unused KV read serialization

[Amaury Chamayou (achamayou)]

Summary

• Remove the unused include_reads option, its default/forwarding plumbing, and the per-key read writer.
• Preserve the zero map-read and read-count wire headers, legacy decoding/replay, snapshots, encryption and security-domain ordering, and main's scalar Version read tracking for OCC.
• Rely on the existing LTS compatibility test for ledger-format backward compatibility, without adding a separate unit test.

Scope

This is a standalone cleanup against main. The diff is exactly four production files, +11/-38; the added compatibility unit test has been removed. It does not include Lean/model, tracing, fuzzer, optional<Version>, or zero-revision/OCC-fix changes.

Validation

Completed after removing the unit test, in an isolated Linux/WSL source tree identical to the committed tree:

• Fresh Debug/Ninja kv_test build.
• ./tests.sh -R '^kv_test$' -L unit --no-tests=error --output-on-failure -V: 74/74 cases and 4,735 assertions passed, with no skips.
• Full scripts/ci-checks.sh -f: all 14 checks passed, with explicit exit status 0 and no source changes.

[Copilot]

🔵 Needs a closer look

It changes core KV ledger serialisation interfaces/behavior (including compatibility-sensitive encoding paths) and should receive final human review despite the added regression coverage.

Pull request overview

This PR removes the unused per-key KV read-set serialisation path (include_reads and serialise_read) while preserving ledger compatibility by keeping the legacy read-set headers (entry version + read-count) in the wire format as zeroed values, and adding regression tests to validate legacy decoding/replay behavior.

Changes:

• Remove the include_reads plumbing from AbstractMap::serialise_changes and related call sites.
• Remove KvStoreSerialiser::serialise_read and the corresponding wrapper implementation.
• Add unit regression coverage asserting byte-identical serialisation for public/private maps, correct sizing, removals, and replay/decoding of legacy entries containing reads.

Custom instructions used:

• .github/copilot-instructions.md
• .github/instructions/reviewing.instructions.md

File summaries

File	Description
src/kv/untyped_map.h	Always emits legacy read headers as {NoVersion, 0} while serialising writes/removes, removing the now-unused per-key read serialisation.
src/kv/test/kv_serialisation.cpp	Adds a compatibility-focused regression test covering byte layout, size projection, legacy read decoding, and replay behavior.
src/kv/kv_types.h	Updates KV serialiser/map interfaces by removing serialise_read and the include_reads argument.
src/kv/generic_serialise_wrapper.h	Removes the concrete serialise_read implementation from the generic serialiser wrapper.
src/kv/committable_tx.h	Simplifies transaction serialisation sizing/encoding paths by removing the unused include_reads parameter propagation.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Lite

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