fix: typecheck without emit, placeholder test, drop build artifacts

Removes composite project references in favor of simpler -p checking.
Adds noEmit to tsconfig so tsc is typecheck-only.
Adds smoke test to unblock CI test gate.
Ignores tsbuildinfo artifacts from git.

.gitignore

@@ -3,3 +3,4 @@ dist/
 data/
 *.log
 .DS_Store
+*.tsbuildinfo