[Device]: K380 action buttons (F4-F7) could not be remapped

### Pre-flight checklist

- [x] I quit **Logi Options+** before testing.
- [x] I searched existing issues for my device.

### Device model

K380

### Connection

Bluetooth (direct, no receiver)

### What's the problem?

Device is detected but a feature doesn't work

### `openlogi list` output

```text
Multi-Device Keyboard K380 (—, vid=046d pid=b342)
└─ slot 255 ● Bluetooth Multi-Device Keyboard K380 (keyboard, wpid=?, battery=50% good (discharging))
model_ids=[b342,0000,0000] ext=00 serial=— unit_id=e3000000 transports=bt
```

### `openlogi diag features` output

```text
device: Bluetooth Multi-Device Keyboard K380 (direct 046d:b342)
idx id ver flags
0 0x0000 v1
1 0x0001 v1
2 0x0003 v1
3 0x0005 v0
4 0x0007 v0
5 0x0020 v0
6 0x1000 v0
7 0x1814 v1
8 0x1815 v0
9 0x1b04 v0
10 0x1e00 v0 hidden
11 0x40a2 v0
12 0x4220 v0
13 0x4521 v0
14 0x4531 v0
(15 feature entries)

fw 0: MainApplication RBK42.01_B0017 pid=b342 extra=c18dbfdd00
fw 1: Hardware HW 00.01_B0000 pid=0000
```

### Details

K380 has action buttons
F1-F3 - multi-device connect
*F4 - Home
*F5 - Alt-Tab
*F6 - Context Menu
*F7 - Back
F8-10 - media buttons
F11-F12, insert - volume buttons

few extra shortcuts is not configurable in-apps but diffs by app, so can be remapped too:
| Shortcut | Legacy Logitech Options | Logi Options+ | Without App |
|---|---|---|---|
| Fn+L | Display off | System Sleep | Should be investigated
| Fn+Tab | PrintScreen | Screenshot | PrintScreen |
| ... | ... | ... | ... |

Extra [Logi Support](https://support.logi.com/hc/en-ch/articles/360023184954-Shortcut-and-media-keys-for-the-K380-keyboard) topic present

buttons F4-F7 allowed to be remapped in Logi Options+ app to custom actions

~also as a dup of https://github.com/AprilNEA/OpenLogi/issues/865 - Logi Options+ has option to make F-keys act like F-keys and action keys will be invoked via Fn+F-key~

F-row remap is merged in https://github.com/AprilNEA/OpenLogi/pull/395
But K380-specific actions still need GUI positioning and Agent investigation

OpenLogi

Logi Options+

Start by reviewing the existing F-row remap work in pull request #395 and inspect the K380 output from `openlogi list` and `openlogi diag features`. Investigate the Agent handling and GUI positioning for the K380-specific actions. Done means F4-F7 appear in the K380 interface and can be assigned custom actions.

Written by the indexing model from the issue text.