Fix autofetch: retrigger Start, preserve frame bytes, add control connection to stop freerun

[mikelangmayr]

• Bumps hispec_tracking_camera submodule to Fix autofetch: retrigger Start, preserve frame bytes racing a reply hispec-tracking-camera-instrument#14, which retriggers Start after power on so FASTAUTOFETCH actually streams (root cause of autofetch always returning 0 of N frames)
• send_cmd() now routes <QF frame bytes that race a command's own reply into a new autofetch_carryover buffer instead of discarding them, since read_autofetch_frame() needs every byte
• Adds a dedicated archon_control connection so autofetch_mode 0 can reliably stop autofetch/freerun even while the primary connection is actively flooded with unsolicited <QF data — previously this required a manual second socket and a camerad restart
• See plans/AUTOFETCH-TESTING-PLAN.md for the full debugging writeup and verification steps run on real hardware