Allow repeated speed-mileage time-segmented schemes to use either the original start-boundary timestamp form or the segment-end timestamp form emitted by older clients.
For RSMT schemes whose first time segment starts at zero, keep switching against the next segment boundary. For schemes whose first time is non-zero, treat each timestamp as the current segment's end time so payloads such as 120/240/360 are accepted and scheduled correctly.
Defer eligible time-segment changes until the track mileage reaches the configured line-length boundary after movement, matching the legacy app-track behavior that avoided mid-line speed pattern changes.
Add runtime tests covering line-end switching and non-zero first time segment acceptance.
Verification: cmake --build build && ctest --test-dir build --output-on-failure
crosstyan
5ed07253d8