Add presenter seeking

[mprib]

Parent

Sub-issue of #885 (Video Playback Architecture Refactor)

Goal

Add video playback controls to the presenter for interactive frame selection.

Update Presenter

src/caliscope/gui/presenters/intrinsic_calibration_presenter.py

Add methods:

• seek_to(frame_index: int) -> None — for slider scrubbing
• pause() -> None
• unpause() -> None

Add properties:

• frame_count: int
• current_frame_index: int

Update View

src/caliscope/gui/views/intrinsic_calibration_dev_view.py

• Add slider widget
• Wire slider signals to presenter methods
• Disable controls during COLLECTING/CALIBRATING states

Fix

Legacy slider freeze bug — button disabled at end frame and doesn't recover when seeking backward.

Behaviors

Paused state:

• Slider drag → seek_to() shows tracked frame at position
• Slider release → stays paused at new position

Playing state:

• Slider tracks current frame position
• Slider drag → pause, show tracked frame
• Slider release → resume from new position

During calibration (COLLECTING/CALIBRATING):

• Playback controls disabled
• Cannot interrupt mid-calibration except via Stop button

Verification

Manual testing of slider behavior in all states

Branch Order

5 of 7 in #885

[mprib]

Completed in PR #906