refactor(agent): split the orchestrator tests by what they exercise

orchestrator/tests.rs was 1042 lines: 37 tests over six areas. Each is its own module now — device_list, device_settings, reapply, publication, camera, capture_plans — and tests.rs keeps the imports and the fixtures more than one area uses (the orchestrator and device builders, the inventories). Every child starts with `use super::*`.

Pure move: no test body changed; 37 tests before and after.