[X-F-R]

Summary

Replaces the protobuf-based C++ client SDK on main with a complete port of the litearm Python SDK over the raw serial framing protocol (SOF 0xA5, CRC16-CCITT-FALSE).

The two trees share no git history, so this lands as a whole-tree replacement rather than as a patch on the existing SDK. This branch is parented on main at ff66587 specifically to make the change reviewable as a PR; the diff below is the replacement, and it is large by nature.

Breaks consumers of the previous C++ SDK. include/litearm/arm.hpp, protocol.hpp and transport.hpp are rewritten in place, and codec.hpp, device.hpp, types.hpp and exceptions.hpp are removed along with proto/litearm.proto. Any caller of the current SDK stops compiling. Under this repository's version policy the commit carries no BREAKING CHANGE: marker, so it publishes as a minor.

AGENTS.md is the repository's rule file and this branch does not modify it — it is byte-for-byte main's. Neither does it change LICENSE, .github/workflows/ci.yml, .github/workflows/release.yml, .releaserc.json or .markdownlint.json.

Changes

• Added the serial SDK: include/litearm/ (23 headers), src/ (18 translation units), examples/ (7 programs), tests/ (27 binaries), plus build.sh, env.sh, run_example.sh and the PowerShell equivalents.
• Added cmake/litearmConfig.cmake.in, cmake/litearm.pc.in and cmake/toolchain-aarch64-linux-gnu.cmake for find_package, pkg-config and aarch64 cross builds.
• Added TROUBLESHOOTING.md and UNVERIFIED_REGISTER.md, the latter listing 22 inherited gaps each with a file:line reference and machine-checked by tests/test_register.cpp.
• Documentation is English, per the repository's documentation standard: README.md, docs/DEVELOPER_GUIDE.md, TROUBLESHOOTING.md, UNVERIFIED_REGISTER.md and examples/README.md. The Chinese developer guide is kept as docs/DEVELOPER_GUIDE.zh-CN.md, matching the existing README.zh-CN.md convention. Source comments stay Chinese, following the upstream Python reference.
• Removed with the previous SDK: proto/litearm.proto, the codec, device, types and exceptions layers, tests/test_arm.cpp, test_arm_direct.cpp, test_codec.cpp, test_device.cpp, and docs/DEVELOPER_GUIDE.zh-CN.md (superseded by the port's own guide under that name).
• Merged .gitignore is the union of both files, so neither side's build artifacts become trackable.
• Corrected rotted README.md line references in the register, a table-of-contents entry that contradicted its own heading, and a load-sensitive 10 ms timeout in two test_precheck cases.

Testing

The suite was run on this branch after the commits and before the push:

$ ./build.sh                     100% tests passed, 0 tests failed out of 27
$ ./build.sh --clean --werror    100% tests passed, 0 tests failed out of 27
$ ./build.sh --clean --asan      100% tests passed, 0 tests failed out of 27
$ ./build.sh --clean --tsan      100% tests passed, 0 tests failed out of 27

All four print:
The following tests did not run:
	 21 - test_protocol_sync (Skipped)

test_protocol_sync is skipped, not passing. It cross-checks the protocol constants against the firmware sources, which sit behind Gitee enterprise permissions. The skip is pre-existing and unrelated to this change; it is recorded as item 15 in UNVERIFIED_REGISTER.md.

--werror is this repository's baseline: the library compiles under -Wall -Wextra with zero warnings.

One real failure was found and fixed while preparing this branch. Under the full TSan run, test_precheck failed with not arrived, timed out 0.0s; the cause was a 10 ms arrival window that only holds on an unloaded machine (the same binary passed 10 out of 10 standalone). The two cases now use the default timeout like every other call site. TSan also reports a large batch of data races and double-lock warnings here; those are documented in README.md as false positives backed by runtime lock-discipline assertions, and they are unchanged by this branch.

The hardware claims in the commit message come from a separate real-arm session on firmware Litearm1.8.0-7J, reported in full in the accompanying verification report. They are not reproducible from CI, because the probes used are not committed.

Issues

None. No issue is referenced and this PR closes nothing.

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🎉 This PR is included in version 0.1.0 🎉

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