- fpga_target gains max_tck_khz (registry key), the max safe JTAG TCK
for a part/board (0 = unspecified)
- jtag_autoinit, after identifying the chain, resolves the clock: if the
requested JTAG_TCK_FREQ_KHZ exceeds the smallest device max, it clamps
it and re-opens the probe once (stored probe id) to apply, then
re-scans; within-cap / unset just report the cap
- autoinit body extracted into autoinit_run() so it can re-run after the
re-tune; fpga_list shows maxtck
Validated on the IGLOO2/FlashPro (req 500 -> clamp 200 -> reopen -> still
detected; within-cap and unset paths don't reopen).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>