## Bug Description

The `Style > Corners > Round` option in the Omarchy menu does not work. Clicking it produces no visible change and no notification.

## Root Cause

Two issues in the toggle system:

### 1. Wrong file extension
`omarchy-hyprland-toggle` hardcodes `.lua` extension:
```bash
FLAG_SOURCE="$OMARCHY_PATH/default/hypr/toggles/$FLAG_NAME.lua"
```

But the actual file is `rounded-corners.conf` (not `.lua`), so the script fails with:
```
Flag not found: rounded-corners
```

### 2. Invalid Lua format
Even if the file is found, `rounded-corners.conf` uses plain Hyprland config syntax:
```
decoration {
    rounding = 6
    rounding_power = 3
}
```

But the toggles system loads files as Lua modules via `require_all.files()`. Other toggle files (like `window-no-gaps.lua`) correctly use:
```lua
hl.config({
  decoration = {
    rounding = 0,
  },
})
```

## Expected Behavior

Clicking `Style > Corners > Round` should:
1. Copy the toggle file to `~/.local/state/omarchy/toggles/hypr/`
2. Apply `rounding = 6` and `rounding_power = 3`
3. Show notification "Round corners enabled"

## Actual Behavior

1. Script fails with "Flag not found: rounded-corners"
2. No file is copied
3. No notification is shown
4. Rounding remains at 0

## Reproduction

1. Open menu with `Super+Alt+Space`
2. Go to `Style > Corners`
3. Select `Round`
4. Observe nothing happens

## Environment

- Omarchy version: 3.8.2
- Hyprland: Latest

## Suggested Fix

Either:
- Rename `rounded-corners.conf` to `rounded-corners.lua` and convert to Lua format with `hl.config({...})`
- Or update `omarchy-hyprland-toggle` to try multiple extensions (`.lua`, `.conf`)