build(internal): add test compilation check to package builds

[dreamorosi]

Summary

Changes

Package builds only compile source code under src/; test files under tests/ were never type-checked, so type errors in tests could go unnoticed until runtime. This PR adds a dedicated test type-checking step so those errors are caught in CI.

• build:tests script added to each package (tsc --noEmit -p tests/tsconfig.json).
• build:tests is intentionally NOT wired into the regular build — day-to-day builds stay fast and never emit test files into the published bundle.
• CI runs the type-check as a dedicated step (Type check tests) in the code-quality matrix job, after dependencies are installed and the whole workspace is built (so every package's lib/ exists for cross-package import resolution).
• Created the missing tests/tsconfig.json for jmespath (the only package without one).
• Fixed pre-existing test type errors surfaced by the new check:
  • commons — deepMerge.property.test.ts (invalid depthSize on fc.array constraints → size) and deepMerge.test.ts (typed the result of deepMerge({}, source)).
  • metrics — basicFeatures.decorator.test.functionCode.ts (made the decorated handler async so it satisfies HandlerMethodDecorator).

Notes for reviewers

• The original proposal suggested wiring build:tests into build in parallel (& npm run build:tests). That is unsafe here: the test type-check resolves cross-package imports against each dependency's built lib/, but the workspace build order builds some dependencies (e.g. testing) after their consumers, and the parallel & also races a package's own emit build. Running it as a separate CI step after the full build avoids the race entirely.
• The proposal also suggested removing ../src/**/* from tests/tsconfig.json. That cannot be done here: the configs inherit composite: true, which makes TypeScript enforce TS6307 ("Projects must list all files or use an include pattern"). The source glob is kept (including in the new jmespath file).
• Maintainer caveat (tests must not end up in the published npm bundle) holds: the emitting builds use rootDir: ./src + include: ["./src/**/*"], build:tests uses --noEmit, and it is not part of the regular build. Verified no test files land in any lib/ output.
• Verified locally: emit-only npm run build passes, and npm run build:tests -w <pkg> passes for every package after a full build.

Issue number: closes #5073

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[svozza]

Can we add the check to the pre-commit hook so we don't have to wait until the CI fails if we forget to run it locally?

[dreamorosi]

Can we add the check to the pre-commit hook so we don't have to wait until the CI fails if we forget to run it locally?

Good point - added, but to pre-push in line with when we run the other tests.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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