Camera clock columns added from clip-specific wallclock anchors.

Columns added to the master transcript export:
- camera_clock_date
- camera_clock_time

Method:
1. Read clip-specific corrected wallclock anchors from corrected_master_reference-oai.csv.xlsx.
2. For each clip, compute a stable clip base time:
   clip_base = corrected_wallclock_start - video_start
3. For each transcript row, compute:
   camera_clock_datetime = clip_base + clip_timestamp
4. Export the date and time components as two new columns.

Derived clip base times:
- 01_011400_lightfoot_x60ac977d: 2025-12-16 01:14:26
- 02_012000_scalise_x60ac521m: 2025-12-16 01:19:50
- 03_012400_lowery_x60ac328f: 2025-12-16 01:23:42
- 04_012500_rogers_x60ac316h: 2025-12-16 01:24:39
- 05_012600_lightfoot_po5123: 2025-12-16 01:26:51
- 06_012900_rogers_x60ac316h: 2025-12-16 01:29:17
- 07_033200_lightfoot_x60ac977d: 2025-12-16 03:32:25