Keyboard shortcuts don't propagate from embedded EC to EW/ED.

### Steps to reproduce

1. Start an embedded EC
2. Press the mute button or something, such that the EC iframe has keyboard focus.
3. Hit cmd/ctrl-K or some other keyboard shortcut within EW/ED.
4. Nothing happens.

### Outcome

#### What did you expect?

Keyboard shortcuts like cmd/ctrl-K or even cmd/ctrl-/ should work even if you're in a room where EC is present. The iframe should somehow bubble the keyboard events up to the parent app - either explicitly over postmessage or implicitly by not trapping the events (i forget if you can do that cross-iframe).

#### What happened instead?

Keyboard shortcuts appear to just stop working, which feels flakey and crap.

### Operating system

macOS

### Application version

nightly

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

No

Start by reproducing the issue with an embedded EC iframe focused, then trace how keyboard shortcuts are handled in the EC frame and the EW/ED parent app. The work is done when shortcuts such as cmd/ctrl-K and cmd/ctrl-/ still trigger in EW/ED while EC has focus, with suitable coverage for the iframe case.

Written by the indexing model from the issue text.