Proposal, not a bug report, and deliberately not a PR: I could not make a widget-side reskin that was worth shipping (see below), so this is a design question first.

Follows on from #8845 (icons are only tinted when the name ends in `-symbolic`) and #8159 (colorization cannot lighten a dark fill). #8844 and #7288 are the neighbouring cases.

## What happens today

- `omarchy.tray` tints an icon only when its name ends in `-symbolic`.
- Chromium publishes its tray icon as a raw bitmap with no `IconName` at all, so **every Electron tray app is structurally excluded** from tinting (ChatGPT, Proton Pass, Slack, Discord, Spotify, ...). D-Bus dump in #8845.
- The widget's only colour maths is `MultiEffect.colorization` (`rgb = ink * luma(src)`, alpha untouched). It cannot lighten a dark source (#8159) and cannot preserve the detail inside a tile-shaped bitmap, so "tint everything" is not available either.
- `SystemTrayItem.id` is the SNI `Id`, and Chromium hardcodes `chrome_status_icon_1` for all of them, so a per-app setting cannot address them individually.

Result: on a monochrome bar, a couple of brand-coloured icons that nothing in the shell can do anything about.

## Proposal

1. **A tray setting** (name to your taste - `monochrome`, `trayMonochrome`, or a `tray.iconStyle` enum) that, when enabled, prefers a monochrome rendering of any tray item that offers one and draws it in the bar ink. Existing `-symbolic` tinting stays as it is.

2. **A documented app-side contract**, because the widget cannot manufacture a monochrome icon: an app opts in by publishing an `IconName` that resolves in the icon theme (with a `-symbolic` variant) rather than a bitmap alone. That is the half that belongs to app producers - realistically a request to Chromium, since its behaviour is what forces every Electron app to ship a pixmap.

3. **Leave icons untouched when no monochrome form exists** - do not synthesise one. Of the three options I measured, a coloured but recognisable icon is the least bad.

## Why not a patch from me

I built and measured all three renderings on a real bar (flat silhouette, ink x luma, and luminance-normalise-then-ink). The best lands on the bar ink with the detail preserved, but it is still the widget inventing artwork the app never supplied, and at 12px it reads worse than the app's own icon. I reverted it and left the stock widget in place rather than send a reskin - happy to test whatever direction you prefer instead.

## Questions

- Do you want the setting at all, or is the intended answer "icon theme / app side only, no widget change"?
- If yes: does the contract belong in the tray widget, in the icon theme convention, or in the plugin API so other bar widgets can honour it too?
- Any preference on naming (`monochrome` vs `iconStyle`)?

Happy to verify a patch on omarchy 4.0.3 / quickshell 0.3.1 / Qt 6.11.2 (Arch + Hyprland, transparent bar), with real tray items rather than a mock.