fix: Accurate game clock and correct segment highlight dispatch

[JRemitz]

Summary

• Clock accuracy: on_tick() assumed exactly 100ms between Qt timer fires, causing the game clock to drift fast. Now uses QElapsedTimer to measure actual wall-clock elapsed time with remainder tracking so fractional tenths aren't lost.
• Segment highlights: The highlights button always ran reeln game highlights regardless of the "Game Finished" checkbox state. Now correctly dispatches reeln game segment <N> (integer period number) when unchecked, and reeln game highlights when checked. Hotkey follows the same logic.
• Button label: Now includes the period number (e.g. "Generate Period 1 Highlights") for clarity.

Test plan

• Start a game clock, let it run for 60 real seconds — verify the displayed clock matches wall time
• With "Game Finished" unchecked, click highlights button — verify CLI job shows reeln game segment 1 (not reeln game highlights)
• Advance to OT, click highlights button — verify CLI job shows reeln game segment 4
• Check "Game Finished", click highlights button — verify CLI job shows reeln game highlights
• Verify highlights hotkey follows the same dispatch logic

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