A/B in a live lagging shell: disabling fish_autosuggestion_enabled cures
the lag instantly, and re-enabling does NOT bring it back — the toggle
resets the wedged reader state. __autosuggestion_unwedge (fish_postexec)
now applies that reset after every command, at the moment TUIs exit.
Builtins only, invisible, respects a deliberate manual disable. Flight
recorder stays armed until the hook is proven in real use.
Also from this investigation: wedged-thread evidence (sampler attach
cures), lag-sample tool, flight recorder in the zellij fish wrapper.
