Support Ubuntu GNOME setup and native Overlay

[Anuraj-dev]

Problem

On Ubuntu 26.04 GNOME Wayland, voisu setup rejected the session, both packaged user services could fail before ExecStart with status=218/CAPABILITIES, and GNOME could not display the layer-shell capsule.

Result

• Detects the exact Ubuntu 26.04 GNOME Wayland Setup Profile before prompting.
• Preserves the existing Local or Cloud credential wizard and saved configuration.
• Enables and starts the daemon, with a truthful next-login fallback when immediate startup is unavailable.
• Ships a GNOME Shell 50 extension that renders the native Voisu capsule from daemon state.
• Gives Voisu deliberate ownership of configurable Ctrl+Space on Ubuntu. Users can change the extension setting later.
• Prevents the daemon portal shortcut path and notification-only GTK observer from competing with the Ubuntu extension.
• Reports daemon, Overlay, Trigger Key, restart-required, and broken-extension states through setup and doctor.
• Removes the four user-service directives responsible for Ubuntu 218/CAPABILITIES failures from both packaged units while preserving the remaining sandboxing.

Verification

• cargo check --locked -p voisu-app
• focused Ubuntu lifecycle, setup-profile, service-policy, doctor, and service CLI tests
• Node capsule, response-bound, Toggle rejection, and request-generation tests
• Rust formatting and diff checks
• GSettings schema, GNOME metadata, JavaScript syntax, and packaging shell validation

Live Ubuntu 26.04 GNOME package installation, logout/login activation, and capsule rendering remain real-host gates. The full workspace run was not repeated after the host previously returned Disk quota exceeded; the affected focused suites pass.