COMPLETED

Test: TestUserFunctionShadowingNoImport
Status: PASS (all 4 subtests)
Coverage: User-defined functions with stdlib names (ReadFile, Atoi) do NOT trigger imports
Verification: GetNeededImports() output checked directly at ErrorPropProcessor level
Lines Added: 150 lines in preprocessor_test.go (lines 1174-1323)
Test Run: go test ./pkg/preprocessor -run TestUserFunctionShadowingNoImport -v
Result: PASS (0.00s)

Issue #3 (IMPORTANT-1) verified: Only qualified calls (os.ReadFile) trigger imports, not bare function calls (ReadFile).
