### System details

AMD Ryzen AI 7 350 w/ Radeon 860M / AMD Radeon 860M Graphics
Omarchy 4.0.0-1
Webcam: `USB2.0 FHD UVC WebCam` (uvcvideo driver)

### What's wrong?

`omarchy screenrecord --with-webcam` starts the webcam overlay via `mpv` with:

```
--demuxer-lavf-o=video_size=1280x720,framerate=30
```

No `input_format` is specified, so ffmpeg's v4l2 demuxer is left to choose the pixel format on its own. On this webcam it picks **YUYV** (raw), which only supports 1280x720 at **5 fps** on this device — even though the same resolution is available at **30 fps in MJPG**. The result is a visibly choppy webcam overlay in every recording, regardless of the `--webcam-size` chosen.

Confirmed by querying the device directly while the overlay's `mpv` process has it open:

```
$ v4l2-ctl -d /dev/video0 --get-fmt-video
Pixel Format      : 'YUYV' (YUYV 4:2:2)
$ v4l2-ctl -d /dev/video0 --get-parm
Frames per second: 5.000 (5/1)
```

Device's own format list (`v4l2-ctl --list-formats-ext -d /dev/video0`) shows MJPG at 1280x720 supports 30fps, while the YUYV variant at the same resolution caps at 5fps:

```
[0] (MJPG-type, compressed):
  1280x720 @ 30fps
[1] 'YUYV' (YUYV 4:2:2):
  1280x720 @ 5fps   <-- what actually gets selected
```

### What's expected

The overlay should request the compressed/MJPG format explicitly so it gets the 30fps mode the hardware actually supports at that resolution, e.g. adding `input_format=mjpeg` to the `--demuxer-lavf-o` string in `omarchy-capture-screenrecording`'s `start_webcam_overlay()`:

```
--demuxer-lavf-o=video_size=1280x720,framerate=30,input_format=mjpeg
```

I tested this manually — killing the running overlay `mpv` process and relaunching it with `input_format=mjpeg` appended immediately fixes it: the device switches to MJPG and reports a real 30fps, and the overlay is visibly smooth instead of choppy.

### Steps to reproduce

1. `omarchy screenrecord --fullscreen --with-webcam` (webcam with a UVC device that has a raw/YUYV mode capped at a low fps for 720p/1080p, alongside an MJPG mode that supports 30fps at the same resolution — common on USB UVC webcams)
2. Watch the webcam overlay bubble — it's visibly laggy/low framerate
3. Confirm with `v4l2-ctl -d /dev/videoN --get-parm` while recording — shows 5fps instead of the requested 30fps

### Suggested fix

In `omarchy-capture-screenrecording`, add `input_format=mjpeg` to the `capture_options` built in `start_webcam_overlay()`, or probe `v4l2-ctl --list-formats-ext` for the pixel format that actually delivers the target fps at the chosen resolution before launching `mpv`.