CLI Bus.unsubscribe has same splice(-1) bug as desktop app

### Description

Same bug as the desktop app's bus — the unsubscribe closure uses `splice(indexOf(handler), 1)` without guarding against indexOf returning -1. A double-unsubscribe removes the wrong handler.

### Steps to reproduce

1. Subscribe two handlers to the same runId via CLI bus
2. Call the first handler's unsubscribe twice
3. Second handler gets removed

### Expected behavior

Double-unsubscribe should be a no-op.

### Actual behavior

`splice(-1, 1)` removes the last element — the wrong handler.

Find the CLI bus implementation and its unsubscribe closure, then compare it with the desktop app's bus behavior described in the issue. Reproduce the two-handler, double-unsubscribe case and verify that the second handler remains subscribed and the repeated unsubscribe is a no-op.

Written by the indexing model from the issue text.