### What happened

Omarchy's three bundled Chromium extensions (`copy-url`, `yt-dlp`, `whatsapp-slim`)
silently fail to load when the selected browser is **Google Chrome**. They are never
registered, never appear in `chrome://extensions`, and no error is shown.

`omarchy-install-browser` copies Chromium's flag file verbatim to Chrome's:

```bash
copy_chromium_flags() {
  mkdir -p ~/.config
  cp -f "$OMARCHY_PATH/config/chromium-flags.conf" "$1"
}

chrome)
  omarchy-pkg-aur-add google-chrome || exit 1
  setup_chromium_policy_directory /etc/opt/chrome/policies/managed
  copy_chromium_flags ~/.config/chrome-flags.conf
```

That file contains:

```
--load-extension=/usr/share/omarchy/default/chromium/extensions/copy-url,/usr/share/omarchy/default/chromium/extensions/yt-dlp,/usr/share/omarchy/default/chromium/extensions/whatsapp-slim
```

**Chrome 137 removed `--load-extension` in Google-branded builds.** It still works in
Chromium and Chrome for Testing, which is why this is invisible to Chromium users.

Upstream announcement:
https://groups.google.com/a/chromium.org/g/chromium-extensions/c/1-g8EFx2BBY/m/S0ET5wPjCAAJ

Chrome 139 additionally removed `--extensions-on-chrome-urls` and
`--disable-extensions-except`.

### What I expected

Either the extensions load under Chrome, or the user is told they will not.

### Steps to reproduce

1. `omarchy install browser chrome`
2. Set Chrome as the default browser
3. Start Chrome, open `chrome://extensions`
4. None of the three Omarchy extensions are listed

Confirmed at the page level — on any YouTube tab, the DevTools console shows the
injected overrides are absent:

```js
MediaSource.isTypeSupported('video/webm; codecs="av01.0.05M.08"')
// true  (an extension that patches this would return "")
```

The process does carry the flag, so the failure is entirely on Chrome's side:

```
/opt/google/chrome/chrome --load-extension=/usr/share/omarchy/default/chromium/extensions/copy-url,...
```

### Practical effect

`SHIFT + ALT + L` (Copy URL from Web App) and the yt-dlp download integration do
nothing for Chrome users. Both are advertised keybindings in
`omarchy menu keybindings --print`.

### Possible directions

- Warn during `omarchy install browser chrome` that bundled extensions are unavailable
- Omit `--load-extension` from `chrome-flags.conf` specifically, since it is inert there
- Ship the extensions through `ExtensionInstallForcelist` in the managed policy
  directory, which `setup_chromium_policy_directory` already creates
- Document `chrome://extensions` → Developer mode → "Load unpacked" as the manual route

Brave and Edge are not Chrome-branded builds and are likely unaffected, but I have
not verified either.

### System

- Omarchy 4.0.4-1
- Google Chrome 153.0.8010.52
- Hyprland 0.56.2, linux-omarchy 7.2.5-3
- Ryzen 7 3700X, RTX 2060 SUPER (nvidia-open 610.57.04)