COMPLETE

Test Function: TestSourceMapOffsetBeforeImports
File: /Users/jack/mag/dingo/pkg/preprocessor/preprocessor_test.go
Lines: 740-796

Test Result: PASS
- Line 1 (< importInsertionLine): NOT shifted ✓
- Line 2 (= importInsertionLine): NOT shifted ✓ [CRITICAL BOUNDARY]
- Line 3 (> importInsertionLine): Shifted correctly ✓
- Line 4 (> importInsertionLine): Shifted correctly ✓

Validates: Task A fix (>= to > change in adjustMappingsForImports)
Prevents: Regression of CRITICAL-1 source map offset bug
