Code-review cleanups: sources, CMake, CI

[mousebrains]

Summary

Cleanups from a code review pass over the sources, build system, and CI. All changes are output-neutral: the integration tests diff converter output against the checked-in reference files and pass unchanged (31/31 locally on macOS, zero build warnings).

Source changes

• Data.C: read the per-record state bits into uint8_t instead of int8_t, so extracting the 2-bit sensor codes no longer relies on implementation-defined right-shift of negative values (the & 0x03 mask made the old code produce identical results on all supported compilers, but the standard didn't guarantee it). Documented the meaning of all four state codes — the silent skip of codes 0 (not sampled) and 3 (unused) previously read like a bug.
• Sensors: removed dead mLength/length() — never read anywhere. Also eliminates a tellg() - spos expression that underflowed to a huge size_t if the stream failed mid-parse.
• SensorsMap.C: build the unknown-CRC exception message with string concatenation instead of a fixed 2 KB snprintf buffer; drop a wrong-direction int cast when inserting into the size_t-valued name map.
• Logger.H: fall back to spdlog's default logger if init() fails twice, so the logging macros can never dereference a null logger.

Build / CI

• src/CMakeLists.txt: stop double-linking spdlog and dbd_common into executables — the PUBLIC links on dbd_common/dbd_netcdf already provide them transitively. Silences the ld: ignoring duplicate libraries warnings on every macOS build. decompressTWR keeps its direct spdlog link since it deliberately avoids dbd_common.
• build-test.yml: include test/decompressTWR in the shellcheck lint step — it was the only test script not being checked (verified it passes shellcheck).
• .claude/settings.json: permission allowlist so Claude Code doesn't prompt for tree-local commands (build, test, lint, local git, project binaries). Drop this commit if you'd rather keep that config out of the repo.

Test plan

• Clean rebuild from scratch (Release, AppleClang): zero warnings
• ctest: 31/31 passing, including reference-file comparison integration tests for all five tools
• shellcheck -s sh test/decompressTWR passes locally

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.02%. Comparing base (6dfeb12) to head (fb5f55d).

Files with missing lines	Patch %	Lines
src/Logger.H	50.00%	1 Missing ⚠️
src/SensorsMap.C	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
- Coverage   63.04%   63.02%   -0.03%     
==========================================
  Files          34       34              
  Lines        3412     3410       -2     
  Branches      423      424       +1     
==========================================
- Hits         2151     2149       -2     
  Misses       1261     1261              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.