[DanielThomas]

Summary

• deduplicate qualified-type candidates discovered during javac tree scanning
• prevent compact record constructors from applying the same source edit twice
• add a regression test covering import normalization for a qualified record component

Testing

• ja test --all (156 tests)
• ja compile --recompile
• ran the fixed source formatter against the Ja source module; the previous five syntax errors are gone

Closes #18