The Phase 2 E2E test was sending the Python GPIO command via
'python3 -c "..."' but bash quote-nesting silently corrupted the
script — the python process started, printed nothing, exited 0, and
the test asserted 'GPIO_SETUP 17 out' was missing in proto bytes
(it never got sent because the python script never ran).
Switch the test to base64-encode the script + pipe through base64 -d
into a file, then execute. Verified end-to-end now:
[test] proto received 36 bytes:
GPIO_SETUP 17 out pud_off
GPIO 17 1
[test] ✓ shim → proto pipeline works
Also bump the rootfs manifest entry to the final Phase 2 build
(d6d4a274 raw / debd1c33 zst, version 2026.05+phase2-shims-final).
Earlier auto-discovery in _transport.py was hanging at import time
on some glob/sysfs interaction. Now hardcoded /dev/vport1p1 which
is the empirical path under -M virt + virtio-blk-pci on slot 0.
ca2b76f1f8