Add the tracking camera exposure script and harden it

[mikelangmayr]

• Bring run_camerad_script.py under version control; it existed only on fei, with one backup in /tmp. First commit is the deployed file verbatim, second is the changes, so the hardening reads as a diff.
• Refuse a window below 50x50 in counted and freerun modes. A 10x10 reads out in about 1 ms, so the detector produces near 1 kHz, the non-autofetch readout cannot keep up, and the unread data wedges the controller. The message names --autofetch and --exptime.
• Replace --Nreads and --nseq with --frames and --repeat. --nseq meant sequences in counted mode but total frames under autofetch.
• Report the rate from one output rather than the sum across outputs, which counted a 500 frame run as 1000 frames at 1697 fps where the truth was 847.
• Default to the instrument config, which loads the same ACF as the instrument build.
• Verified on fei: the guards reject as intended, --frames 3 and --frames 2 --repeat 2 run clean, and autofetch at 300 frames reports 300 at 836 fps.