[svozza]

Summary

Centralise test compiler settings and shared setup declarations so all 16 test projects inherit one configuration. Test type-checking now uses its own incremental caches instead of reusing production build caches.

Changes

• Add tsconfig.test.json, extending the root compiler configuration with test-only overrides, shared setupEnv.ts inclusion, and ${configDir} paths for package sources and tests.
• Disable composite/declaration output for test projects while retaining incremental checking in each workspace's .tsbuildinfo/tests.json.
• Reduce package test configs to the shared base while retaining Kafka's JSON-module override.
• Preserve the layer tests' existing compiler behaviour: allowImportingTsExtensions and resolveJsonModule were previously inherited from layers/tsconfig.json. They are now explicit in layers/tests/tsconfig.json because it extends the shared test base. Its existing include list, including layers/package.json, is unchanged.
• Remove the matcher type test's explicit setup import to verify inherited declarations, and document the configuration conventions.

Validation passed: clean ESM/CJS rebuilds, workspace and layer type-checks, all Vitest type suites, 3,718 unit tests with 100% coverage, and the layer-packaging unit test. Comparison of 48 resolved configurations confirmed no existing input files were dropped; compiler probes verified matcher typing and root-option inheritance across all 16 test projects. All 1,812 production output/cache hashes remained unchanged.

Type-check timings were effectively unchanged: 52.2 → 51.7 seconds cold and 41.1 → 41.1 seconds cached in a single before/after sample.

Issue number: closes #5694

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[dreamorosi]

Nice one!