Mac-on-Linux: implement GTK and desktop-integration lane for sourceos-shell

[mdheller]

Parent tracker: #77

Summary

Implement the GTK and desktop-integration lane required for the Mac-on-Linux realization of sourceos-shell.

Goal

Deliver Linux-facing desktop behavior that approximates or exceeds the agreed Mac-on-Linux UX for:

• menu-bar and menu-model integration where feasible
• window control/titlebar conventions
• desktop-entry and shell registration
• file preview and file-manager affordances
• shortcut overlays and discoverability surfaces

Relevant substrate clues

The org already contains relevant substrate repos such as:

• SociOS-Linux/gtk-mac-integration
• SociOS-Linux/gtk-osx
• SociOS-Linux/nautilus
• SociOS-Linux/gnome-shell
• SociOS-Linux/mutter
• SociOS-Linux/shortcut-overlay

These are not the runtime home for the shell, but they are valid realization or reference surfaces for the Linux integration lane.

Workstreams

1. Toolkit behavior

• GTK/mac integration patterns
• titlebar/window-control behavior
• menu-bar/global-menu feasibility by environment

2. Desktop/file affordances

• file preview / quick-look-like affordances
• file-manager integration expectations
• desktop entry and app identity registration

3. Discoverability

• shortcut overlay alignment with shell-native commands
• visible affordances for Mac-on-Linux behavior differences

Acceptance criteria

• GTK/desktop-integration goals are explicitly documented
• toolkit, file-affordance, and discoverability lanes are separated and trackable
• follow-on Linux realization PRs can reference this issue for GTK/desktop work

Proposed owner

@mdheller

[mdheller]

Current upstream GTK/desktop clue for this lane:

profiles/linux-dev/workstation-v0/gnome/mac-defaults.sh is already present on main and applies a first mac-like GNOME behavior pack, including:

• hot corners off
• 12h clock + weekday/date
• locate-pointer enabled
• Nautilus double-click policy + permanent delete option
• seeded favorites
• Super+E for Files
• Super+Return for Terminal

That means this lane should treat the existing GNOME defaults pack as substrate already in flight rather than re-inventing the first desktop behavior slice. Follow-on work here should focus on desktop/toolkit parity gaps that still remain after that pack.