ExecuTorch counter policy PoC

This signed package is a lifecycle and protocol fixture, not a general GUI model. The 728-byte upstream ExecuTorch add model computes state + 1. Its signed contract maps outputs 1, 2, and 3 to the typed SoloPi click on the SoloPiTddDemo increment button and output 4 to done. The verification engine still requires deterministic Oracles for counter value 3 and status Completed before returning passed.

The package was signed by the offline PoC release key whose public half is stored under solopi-harness-cli/src/solopi_harness/resources/keys. The private key is not present in this repository.