- Adds gh-view-title component to implement mobile menu button for titles on any page
- Refactors the `content-cover` out into the application template
- Fix various z-index issues with content-cover and gh-alert
- Move `.settings-menu-expanded` application view state from body to `.gh-viewport`
- Unify nav menu / mobile menu actions and code
References #5071
- Re-implements the previously broken top notification styles
- Moves the top notification outlet outside the `<main>` to ease styling (we have several nested position fixed/absolute boxes that make this tough - moving the outlet makes it easier)