fix(bus): guard indexOf in InMemoryBus unsubscribe to prevent splice(-1)

[serhiizghama]

Problem

Closes #491.

The desktop app's InMemoryBus (apps/x/packages/core/src/application/lib/bus.ts) builds its unsubscribe closure as:

this.subscribers.get(runId)!.splice(this.subscribers.get(runId)!.indexOf(handler), 1);

indexOf is not checked for -1. If unsubscribe() is called twice (or after the handler is already gone), indexOf returns -1 and splice(-1, 1) silently removes the last handler in the array — a different, still-active subscriber.

Reproduction:

1. Subscribe two handlers a and b to the same runId.
2. Call a's unsubscribe.
3. Call a's unsubscribe again.
4. b is now gone, so it no longer receives published events.

Solution

Guard both the missing-runId entry and the -1 index so a repeated unsubscribe is a true no-op:

const handlers = this.subscribers.get(runId);
if (!handlers) return;
const idx = handlers.indexOf(handler);
if (idx >= 0) handlers.splice(idx, 1);

This matches the pattern already used by the other buses in the same package (background-tasks/bus.ts, knowledge/live-note/bus.ts).

Note: the CLI bus has an identical bug tracked separately in #492 — this PR only touches the desktop app bus for #491.

Testing

Added bus.test.ts covering event delivery, single unsubscribe, and the double-unsubscribe no-op regression.

$ npx vitest run src/application/lib/bus.test.ts
 Test Files  1 passed (1)
      Tests  3 passed (3)

npm run build (tsc) passes.