docs(provenance): clarify approved Classic reuse

[zoeyrose]

Summary

• clarify that extracted tools remain GPL as distributed without imposing a blanket outbound reuse ban
• route exact historical source reuse through the canonical per-contribution grant audit
• distinguish recorded MIT destination reuse from GPL dependency, linking, binary, or bundle approval

Validation

• python3 -m unittest discover -s map-checker-qt/tests -v (20 tests passed)
• python3 -W error -m compileall -q -f map-checker-qt
• git diff --check