* fix(ai-insights): reject success from failed helper processes

Success JSON was accepted without checking the helper exit result in popup generation, model discovery, and wallet operations. Validate successful exits before confirming results and preserve the last confirmed insight.

Add direct adversarial reply checks and production controller/settings regressions. Update Unreleased, the usage guide, and the AI Insights contract. TODO is unaffected: AI Insights is widget-owned and has no macOS parity or official CLI blocker.

* test(settings): allow scheduling margin in secret prompt fixtures

The 0.6-second phase bounds left only 0.15 seconds for Python startup and scheduling and timed out valid late submissions both locally and in PR CI. Use three-second phases with two-second submissions so the combined flow still exceeds one phase, and wait at most two seconds for asynchronous child shutdown.

Cancellation, TERM/KILL escalation, hostile argument quoting, stdin-only secrets and production deadline assertions remain intact. Document the fixture scale in Development. This test-only CI fix has no additional user-visible changelog or TODO impact.