installModule() ended with an unconditional setState(Enabled). Store updates,
zip uploads and plain reinstalls all pass through it, so switching a module off
in the panel survived only until its next update — which is how a disabled plex
came back and then blocked `watch` from being disabled at all.
The admin's choice is now captured before the Installing transition overwrites
it and restored at the end; a first install still enables, since there is no
choice to preserve. stateAfterInstall() reads the raw override rather than
listModules() so the transient Installing / Failed states cannot be mistaken
for a deliberate "disabled".
Restoring that state uses the new writeState() instead of setState(): putting a
module back into the state it already had is a lifecycle transition, not an
admin "disable", and must not be vetoed by the dependents guard — otherwise
updating a disabled `watch` would fail at the last step because `plex` exists.
setState() keeps the guard for the deliberate case.
Three tests cover it; two of them fail against the previous behaviour.
Verified: 860 tests, make gates, CRAP gate.
Divarion_D
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