setup() prints the stored coredump summary on every boot and trusted its
backtrace depth. A half-written dump reads back as the 0xa5 stack fill, so
depth was 0xa5a5a5a5: the loop read past bt[16], snprintf ran past its
256-byte buffer once the size went negative, and the interrupt watchdog
reset the board. The dump stays in flash, so every boot hit it again
(seen 2026-10-21: 162 TG1WDT resets in a row, each stopping after "Cause:").
formatBacktrace() in Utils reads at most bt[]'s 16 frames and stops when the
buffer is full, and the line notes IDF's corrupted flag. The task name is
printed at most 16 chars, since exc_task isn't always terminated.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>