ci(clang-tidy): switch to high-signal whitelist (CoolProp-2uw)

[ibell]

Summary

Tighten .clang-tidy from Checks: '*, -<dropped>' (everything-minus) to a positive whitelist of bug-finding + modernization + perf categories. The clang-tidy CI workflow is informational-only (per #2801), so this config defines what gets surfaced as "interesting" in the artifact — and previously most of it was style noise.

Empirical before/after on representative src/ files

Same docker run as the survey for #2801, this time with the new config:

src/CPstrings.cpp

	Before	After
Warning count	5+	1
Categories	misc-include-cleaner, misc-use-internal-linkage, readability-isolate-declaration, readability-braces-around-statements, modernize-use-emplace	modernize-use-emplace (auto-fixable)

src/Solvers.cpp

	Before	After
Warning count	15+ (cascading)	30
Dominant category	misc-include-cleaner (Eigen::, std::, _HUGE, root_sum_square)	cppcoreguidelines-init-variables (×27)
Other	misc-const-correctness, readability-isolate-declaration	performance-avoid-endl (×2), modernize-deprecated-headers (×1)

The 27× cppcoreguidelines-init-variables cluster is at solver entry points (lines 14, 109, 160, …) — uninitialized doubles in numerical code can cause non-deterministic results. Real signal.

Whitelist categories

• bugprone-*, cert-*, clang-analyzer-*, cppcoreguidelines-*
• modernize-*, performance-*
• readability-implicit-bool-conversion (catches if (n) for integer n; pointer conditions already allowed via existing CheckOption)
• The project's hicpp-* survivors (exception-baseclass, multiway-paths-covered, no-assembler, signed-bitwise)

Dropped categories (high noise on this codebase)

• misc-* — include-cleaner, const-correctness, use-internal-linkage
• readability-* (except implicit-bool-conversion) — isolate-declaration, braces-around-statements, use-concise-preprocessor-directives, etc.
• portability-*, boost-*, fuchsia-*, google-*, zircon-*, abseil-*, llvm*, altera* — irrelevant or noise

Preserved

All existing per-check suppressions (narrowing-conversions noise, override macros, Qt raw pointers, Google Test global vars) are preserved verbatim within the whitelisted categories. Long-standing project knowledge stays intact.

Cleaned up

Dropped dead CheckOptions for now-disabled checks: modernize-use-override.*, cppcoreguidelines-narrowing-conversions.*, misc-non-private-member-variables-in-classes.*.

Test plan

• CI clang-tidy artifact for this PR contains far fewer entries than for prior PRs
• Categories are limited to bugprone-, cppcoreguidelines-, modernize-, performance-, hicpp-* survivors
• The 27 init-variables warnings on Solvers.cpp surface in the artifact (real signal we want)

Related

• Sibling: ci(clang-tidy): document informational-by-design #2801 documents informational-by-design rationale
• Open: ci: add manual-stage clang-tidy pre-commit hook (CoolProp-2uw.6) #2799 (2uw.6, manual-stage clang-tidy pre-commit hook)

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