feat: add tqdm bar to the dataset segment script

[shuheng-liu]

What this does

Add a tqdm progress bar when running src/opentau/scripts/segment_lerobot_dataset.py

How it was tested

Ran src/opentau/scripts/segment_lerobot_dataset.py and observed tqdm bar.

How to checkout & try? (for the reviewer)

Run src/opentau/scripts/segment_lerobot_dataset.py and observe tqdm bar.

Checklist

• I have added Google-style docstrings to important functions and ensured function parameters are typed.
• My PR includes policy-related changes.
  • If the above is checked: I have run the GPU pytests (pytest -m "gpu") and regression tests.

[Copilot]

Pull request overview

This PR adds a progress indicator to the LeRobot dataset segmentation script to make long-running segment jobs easier to monitor.

Changes:

• Add tqdm integration to show a progress bar while segmenting frames.
• Pre-compute total frames across all planned segments to drive the progress bar’s total.
• Update the progress bar once per produced segment based on segment length.

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