[QA][1.x] Build the JNAP contract double and split integration-test tiers

[DevenDucommun]

Purpose

Turn PR #1149 from a classification proposal into a runnable, bounded 1.x test lane. Canonical QA program: https://github.com/linksys/qa-usp-automation

Acceptance criteria

• Co-design the E2E_MOCK contract with the UI team
• Implement a stateful JNAP contract double; force=local is same-origin routing, not a mock backend
• Initialize the plugins/widgets submodule so tests reach execution
• Run and classify the retained mock matrix based on real results; do not assume all proposed 13 flows remain
• Split PR ci: tiered integration testing — per-PR mock tier + nightly device tier [QA proposal] #1149 into a mock/UI-contract PR and a separate device-release PR
• Name the mock lane UI/contract integration, not full end-to-end
• Keep this work bounded to the shipping 1.x line; the 2.x Wasm boundary is tracked separately in [USP][QA] Gate the Dart/WASM boundary and fix subscribe signature drift #1153

Known device-lane blockers

The device workflow still needs config loading and ordering fixes, credential threading, localhost proxy and Linux portability work, plus a release-ref and model/firmware matrix design.