Use pinned Ninja and MSVC recipe for CMake compile_commands.json

[Hannia Valera (hanniavalera)]

Summary

Replaces the CMake section of the generate-compile-commands skill with the precision recipe: pin the Ninja generator, the MSVC compiler, and the in-tree build directory; do not force a build type; and skip the full build.

Why

The MSBuild half of this skill was tuned for reliability, but the CMake half remained a simple cmake -B build -DCMAKE_EXPORT_COMPILE_COMMANDS=ON plus a full build, which leaves four environment-dependent defaults to chance. In an offline evaluation (1,000 attempts: 5 models x 20 iterations x 5 CMake projects x 2 skill variants), the simple recipe matched a fixed reference compile_commands.json on 0.588 of attempts, while the precision recipe matched on 0.950 (three of five models perfect), at about half the tokens and a third the wall time.

What each pin fixes

• -G Ninja: on Windows CMake defaults to a Visual Studio generator, which lays out per-configuration MSBuild files and may not emit a single compile_commands.json. In the evaluation the simple recipe used Ninja only 481 of 500 times; the 19 that did not could not match.
• -DCMAKE_C_COMPILER=cl -DCMAKE_CXX_COMPILER=cl: prevents CMake from selecting a g++/clang on PATH, so every entry uses MSVC.
• -B build: the file must land where the tooling looks (build\compile_commands.json).
• No -DCMAKE_BUILD_TYPE: forcing a type rewrites /Od /RTC1 -MDd on every entry; the reference pins none.
• Configure once and stop: the database is written at configure time, so a full cmake --build adds time and timeout risk without changing it.

Scope

Skill-only change to the ## CMake projects section (56 insertions, 6 deletions). The MSBuild rules and the build-system selection logic are unchanged. Complements the recently merged MSBuild reliability work, bringing the CMake path to parity.