* chore: eliminate all Kotlin compiler warnings in main source
* test(chat): fix cross-class coroutine leaks poisoning the unit suite
- ChatUpdateCommandTest: inject FakeSlashUsageStore — the real DataStore
store inits on real IO threads with a relaxed-mock app (cacheDir NPE)
and leaks an uncaught exception into the next runTest class.
- ChatUpdateCommandTest + SlashCommandDispatchRpcTest: mock
ProfileSwitchCoordinator.switched (ChatViewModelTest pattern) — VMs
otherwise park collectors on the singleton flow that crash later
classes (ProfileSwitchCoordinatorTest) on stale-Main resumption.
Full suite: 944 tests, 0 failures (was 2 flaky per run).
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Co-authored-by: M57 <hy4ri@users.noreply.github.com>
