Wires the new synchronous GPIO Matrix callback exposed by
libqemu-{xtensa,riscv32} 1.1.0 (lcgamboa/qemu commit e178ff5).
Whenever the firmware writes GPIO_FUNCx_OUT_SEL_CFG_REG, the C
plugin now fires picsimlab_gpio_matrix_cb(gpio, signal_id) inline.
The handler:
- Treats signal_id == 0x100 or 0 as "matrix routing cleared" and
emits gpio_routing_clear.
- For LEDC HS/LS range signals (the only ones the frontend
SignalRouter currently consumes), updates the mirror and emits
gpio_routing.
- Drops other signals — the mirror does not need to track them
yet, and emitting them would only fatten WS frames.
Backwards compat:
- Older libqemu (<1.1.0) doesn't expose the new field; the
picsimlab_gpio_matrix_cb placeholder runs (no-op) and the
100 ms _refresh_signal_routing() poll thread continues to feed
the mirror. WS event shape is identical either way.
Burn-in: keeping the poll thread active in parallel with the
callback for now. Once telemetry confirms parity (per phase 4 doc
in velxio-prod/project/esp32-gpio-matrix-cb/), the poll thread
gets retired in a follow-up commit.
437f5f83bc