When a session has browser but not computer (or vice versa), the
behavioral/smoke-test fallback for UI changes was suppressed entirely,
leaving native-desktop (or web) verification guidance undefined. Render
the fallback whenever any visual runtime tool is missing.
Also strengthen the plan-mode tests per review: exercise the iterative
branch gating with iterative:true (previously passed trivially) and
restore a typed Overrides record for the render helper.
Slava Zavadsky
0bbdfe2eaa