fix(qa): align renderer evidence and attribution keyboard assertions

TESTING.md

@@ -218,3 +218,14 @@ While recording, call out anything in these areas — this is the feedback I mos
 - **No planes:** OpenSky data may be momentarily sparse; scroll out or wait a poll cycle.
 - **No GEV MIC button / voice errors:** `OPENAI_API_KEY` didn't load — use the console API for
   the annotation tests and skip the voice-only ones (§2).
+
+
+## Browser harness renderers
+
+The first-run, view-target prewarm, cockpit-plates and floor-hold harnesses
+select Metal on macOS and SwiftShader on other platforms. Cockpit-plates also
+accepts `--swiftshader` on macOS; floor-hold retains `--angle=<backend>`.
+Software runs validate their assertions but do not establish real-GPU visual
+correctness. Floor-hold retains both mesh and DEM checks: an unavailable mesh
+oracle fails the run even when the DEM check passes. Record the backend with
+any screenshots and run GPU visual checks separately when needed.