A 1024-byte oled.show() writevto generates ~1025 calls into
_on_i2c_event, one per byte. The previous code called _log (stderr
write+flush) AND _emit (stdout JSON write+flush) for every event,
saturating the worker subprocess's stdout pipe. The QEMU thread blocks
on the synchronous write, the firmware's ESP-IDF i2c_master ISR
re-enters before the previous one finished, and the Interrupt watchdog
trips on CPU1 with a "Guru Meditation Error: Interrupt wdt timeout"
panic on the second consecutive oled.show() call.
I2CWriteSink already buffers writes internally and emits a single
i2c_transaction event on FINISH, so the per-byte log+emit was pure
overhead with no observability value for display drivers (SSD1306,
PCF8574). Keep them for everything else.
Verified end-to-end via chrome devtools MCP:
- Test minimal (init + 1 explicit show): markers OK, no panic
- Loop test (10x oled.show() + sleep(0.5)): DONE_LOOP, no panic
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