* Fix ESP32-S3 USB CDC: post-disconnect task-WDT reboot from blocking console log writes
When a serial API client disconnects (USB cable still attached), the host
stops draining the USB-Serial/JTAG CDC buffer. The next raw-text debug log
write can then block the main loop task indefinitely (measured: a single
write blocked 52.4 s). The loop task stops feeding the app task watchdog
(APP_WATCHDOG_SECS = 90 s, trigger_panic), so the device reboots with
esp_reset_reason = ESP_RST_TASK_WDT ~97 s after every serial disconnect.
On 2.7.x (arduino-esp32 2.x / IDF 4.4) the reboot also re-enumerated USB;
since the Arduino 3.x migration the reboot is silent (USB stays enumerated),
making it look like a random reboot ~90 s after using the CLI.
Fix: on USB CDC targets, keep console TX in non-blocking mode (txTimeout 0,
drop-oldest) whenever no API client is provably alive, and restore the
normal bounded timeout while a client is connected so protobuf API frames
are never truncated. Toggle points: boot, handleToRadio (host sent bytes),
and onConnectionChanged (set non-blocking before disconnect handling emits
more log lines to a dead port).
Repro/validation on HELTEC_WIRELESS_TRACKER_V2 (macOS + Linux hosts):
open+close any meshtastic-python session, wait 150 s: reboot_count +1 every
time on unpatched builds; flat with this fix. Max observed log write stall
drops from 52405 ms to 30 ms.
* Condense comments per review feedback
---------
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
