Add `runner/helpers/replay_mode.py` (NullFrameSink, NullFcInboundEmitter,
default_frame_period_ms, load_replay_json, resolve_replay_subdir,
imu_replay_noop) and rewire all 13 scenarios off their local
`_resolve_*` / `_drive_*` / `_push_*` NotImplementedError stubs.
Closes the offline FDR-replay execution path. `grep raise
NotImplementedError` under `e2e/tests/` now returns zero matches. +17
unit tests (626 total, up from 608). Unit-test behaviour unchanged
(scenarios still skip via b75 sitl_replay_ready gate when
E2E_SITL_REPLAY_DIR is unset).
Co-authored-by: Cursor <cursoragent@cursor.com>
Oleksandr Bezdieniezhnykh