drawers: restore focus to previous window on dismiss

[1letme]

Fixes #1322

What this does

When a drawer (launcher, session, sidebar, dashboard) is opened via HyprlandFocusGrab, it takes keyboard focus from the active window. Previously, when the drawer was dismissed (via Escape, keybind toggle, or clicking outside), focus was not restored to the previously active window. Hyprland would then fall back to focusing whatever window happened to be under the mouse cursor.

This patch stores the active toplevel's address when the focus grab activates, and dispatches focuswindow to restore it when the grab deactivates.

How it works

• onActiveChanged handler on the existing HyprlandFocusGrab
• When active becomes true: saves Hypr.activeToplevel.lastIpcObject.address
• When active becomes false: dispatches focuswindow address:0x{saved} to restore focus
• If the saved window was closed while the drawer was open, the dispatch is silently ignored by Hyprland and focus falls back to the default behavior (no regression)
• When an app is launched from the launcher, focus is briefly restored to the previous window, then the newly spawned window takes focus naturally

Breaking changes

None.

Side effects

This also restores focus after dismissing the session menu, sidebar, and dashboard, not just the launcher. This should be the expected behavior for all of these.

[soramanew]

This is not a bug with Caelestia, it is simply how Hyprland focus grabs behave by default. Your mouse will still change the window focus if you move it to hover over another window while the focus grab is active, just that it will not receive mouse events.

Hmm, actually I see what you mean. Even if you don't move the mouse it won't focus back the original window if your mouse if over another. But this is still an issue with Hyprland, not Caelestia.