Covers all 19 new _handle_export_* handlers: parametrized success /
kicad-cli-not-found / subprocess-failure paths, plus validation
(missing output, unresolvable board, missing schematicPath) and
detailed flag-construction assertions for gerbers/drill/ipc2581.
Subprocess + filesystem are mocked; no real kicad-cli or board touched.
64 tests.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
