chore(prototype): remove GUI position flip; MovePath exchange refused on both threads

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/research/vehicle-probe.md

@@ -84,3 +84,10 @@ Scanned: the 9 mods in `C:\Users\Public\mod.io\10640\mods\` (e.g. `devers_1`, `m
 ## Segment rebuild dropped (2026-10-05)
 
 The human confirmed in game what the log showed: rebuilding the segment under a held-back vehicle does not get it past the blocker on a single-lane road. The rebuild code is removed from the probe (it's still in git history, last in commit 5d3a254). The lane split after rebuilds on multilane roads (see above) is left as an observation for the multilane ticket, not pursued here.
+
+## Position flip via `MovePath` exchange on the GUI thread (run 2026-10-05 ~21:23 UTC)
+
+- On the GUI thread (`guiUpdate`, with a callback), `api.cmd.sendCommand(api.cmd.debug.makeComponentExchangeCmd(follower, leaderMovePath), cb)` fails with the **same** `Error decoding argument #3: The lua object can't be cast to desired type`, and the callback is never reached. Debug mode was active.
+- So the error is not about callbacks or threads: **the exchange refuses a `MovePath`**, consistent with its doc comment (`EmissionEmitter` or `ModelInstanceList` only).
+- **Conclusion: no script API can write a road vehicle's position or route.** Moving a vehicle past another (jump, flip, teleport) is impossible for line vehicles. The only exception is `jumpToDepotEntity`, which can only target a depot.
+- The probe retried every frame (5951 errors) because the error came before the counter was incremented. The experiment is removed, and the probe is logging-only again.